You (Might) Don’t Need jQuery

Frontend environments evolve rapidly nowadays and modern browsers have already implemented a great deal of DOM/BOM APIs which are good enough for production use. We don’t have to learn jQuery from scratch for DOM manipulation or event handling. In the meantime, thanks to the spread of frontend libraries such as React, Angular and Vue, manipulating the DOM directly becomes anti-pattern, so that jQuery usage has never been less important. This project summarizes most of the alternatives in native Javascript implementation to jQuery methods, with IE 10+ support.

ℹ️ Notice: 1. jQuery is still a great library and has many valid use cases. Don’t migrate away if you don’t want to! 2. The alternatives are not completely equivalent in all scenarios, and it is recommended that you test it before using it.

Translations
Query Selector
CSS & Style
DOM Manipulation
Ajax
Events
Utilities
Promises
Animation
Alternatives
Browser Support

Translations

Query Selector

In place of common selectors like class, id or attribute we can use document.querySelector or document.querySelectorAll for substitution. The differences lie in:

document.querySelector returns the first matched element
document.querySelectorAll returns all matched elements as NodeList. It can be converted to Array using Array.prototype.slice.call(document.querySelectorAll(selector)); or any of the methods outlined in makeArray
If there are no elements matched, jQuery and document.querySelectorAll will return [], whereas document.querySelector will return null.

Notice: document.querySelector and document.querySelectorAll are quite SLOW, thus try to use document.getElementById, document.getElementsByClassName or document.getElementsByTagName if you want to get a performance bonus.

1.0 Query by selector

// jQuery
$('selector');

// Native
document.querySelectorAll('selector');

1.1 Query by class

// jQuery
$('.class');

// Native
document.querySelectorAll('.class');

// or
document.getElementsByClassName('class');

1.2 Query by id

// jQuery
$('#id');

// Native
document.querySelector('#id');

// or
document.getElementById('id');

// or
window['id']

1.3 Query by attribute

// jQuery
$('a[target=_blank]');

// Native
document.querySelectorAll('a[target=_blank]');

1.4 Query in descendants

// jQuery
$el.find('li');

// Native
el.querySelectorAll('li');

1.5 Sibling/Previous/Next Elements

All siblings

// jQuery
$el.siblings();

// Native - latest, Edge13+
[...el.parentNode.children].filter((child) =>
child !== el
);
// Native (alternative) - latest, Edge13+
Array.from(el.parentNode.children).filter((child) =>
child !== el
);
// Native - IE10+
Array.prototype.filter.call(el.parentNode.children, (child) =>
child !== el
);

Previous sibling

// jQuery
$el.prev();

// Native
el.previousElementSibling;

Next sibling

// jQuery
$el.next();

// Native
el.nextElementSibling;

All previous siblings

// jQuery (optional filter selector)
$el.prevAll($filter);

// Native (optional filter function)
function getPreviousSiblings(elem, filter) {
var sibs = [];
while (elem = elem.previousSibling) {
      if (elem.nodeType === 3) continue; // ignore text nodes
      if (!filter || filter(elem)) sibs.push(elem);
}
return sibs;
}

All next siblings

// jQuery (optional selector filter)
$el.nextAll($filter);

// Native (optional filter function)
function getNextSiblings(elem, filter) {
        var sibs = [];
        var nextElem = elem.parentNode.firstChild;
        do {
            if (nextElem.nodeType === 3) continue; // ignore text nodes
            if (nextElem === elem) continue; // ignore elem of target
            if (nextElem === elem.nextElementSibling) {
                if (!filter || filter(elem)) {
                    sibs.push(nextElem);
                    elem = nextElem;
                }
            }
        } while(nextElem = nextElem.nextSibling)
        return sibs;
  }

An example of filter function:

```js
function exampleFilter(elem) {
switch (elem.nodeName.toUpperCase()) {
case 'DIV':
return true;
case 'SPAN':
return true;
default:
return false;
}
}

1.6 Closest

Return the first matched element by provided selector, traversing from current element up through its ancestors in the DOM tree.

// jQuery
$el.closest(selector);

// Native - Only latest, NO IE
el.closest(selector);

// Native - IE10+
function closest(el, selector) {
  const matchesSelector = el.matches || el.webkitMatchesSelector || el.mozMatchesSelector || el.msMatchesSelector;

  while (el) {
  if (matchesSelector.call(el, selector)) {
      return el;
  } else {
      el = el.parentElement;
  }
  }
  return null;
}

1.7 Parents Until

Get the ancestors of each element in the current set of matched elements, up to but not including the element matched by the selector, DOM node, or jQuery object.

// jQuery
$el.parentsUntil(selector, filter);

// Native
function parentsUntil(el, selector, filter) {
  const result = [];
  const matchesSelector = el.matches || el.webkitMatchesSelector || el.mozMatchesSelector || el.msMatchesSelector;

  // match start from parent
  el = el.parentElement;
  while (el && !matchesSelector.call(el, selector)) {
  if (!filter) {
      result.push(el);
  } else {
      if (matchesSelector.call(el, filter)) {
        result.push(el);
      }
  }
  el = el.parentElement;
  }
  return result;
}

1.8 Form

Input/Textarea

// jQuery
$('#my-input').val();

// Native
document.querySelector('#my-input').value;

Get index of e.currentTarget between .radio

// jQuery
$('.radio').index(e.currentTarget);

// Native
Array.from(document.querySelectorAll('.radio')).indexOf(e.currentTarget);
or
Array.prototype.indexOf.call(document.querySelectorAll('.radio'), e.currentTarget);

1.9 Iframe Contents

$('iframe').contents() returns contentDocument for this specific iframe

Iframe contents

// jQuery
$iframe.contents();

// Native
iframe.contentDocument;

Iframe Query

// jQuery
$iframe.contents().find('.css');

// Native
iframe.contentDocument.querySelectorAll('.css');

1.10 Get body

// jQuery
$('body');

// Native
document.body;

1.11 Attribute getter and setter

Get an attribute

// jQuery
$el.attr('foo');

// Native
el.getAttribute('foo');

Set an attribute

// jQuery
$el.attr('foo', 'bar');

// Native
el.setAttribute('foo', 'bar');

Get a data- attribute

// jQuery
$el.data('foo');

// Native (use `getAttribute`)
el.getAttribute('data-foo');

// Native (use `dataset` if only need to support IE 11+)
el.dataset['foo'];

1.12 Selector containing string (case-sensitive)

// jQuery
$("selector:contains('text')");

// Native
function contains(selector, text) {
var elements = document.querySelectorAll(selector);
return Array.from(elements).filter(function(element) {
    return RegExp(text).test(element.textContent);
});
}

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CSS & Style

2.1 CSS

Get style

// jQuery
$el.css('color');

// Native
// NOTE: Known bug, will return 'auto' if style value is 'auto'
const win = el.ownerDocument.defaultView;

// null means not to return pseudo styles
win.getComputedStyle(el, null).color;

Set style

// jQuery
$el.css({ color: '#f01' });

// Native
el.style.color = '#f01';

Get/Set Styles

// jQuery
$el.css({ color: '#f01', 'border-color': '#f02' })

// Native
Object.assign(el.style, { color: '#f01', borderColor: '#f02' })

Add class

// jQuery
$el.addClass(className);

// Native
el.classList.add(className);

Remove class

// jQuery
$el.removeClass(className);

// Native
el.classList.remove(className);

has class

// jQuery
$el.hasClass(className);

// Native
el.classList.contains(className);

Toggle class

// jQuery
$el.toggleClass(className);

// Native
el.classList.toggle(className);

2.2 Width & Height

Width and Height are theoretically identical, take Height as example:

Window height

// window height
$(window).height();

// without scrollbar, behaves like jQuery
window.document.documentElement.clientHeight;

// with scrollbar
window.innerHeight;

Document height

// jQuery
$(document).height();

// Native
const body = document.body;
const html = document.documentElement;
const height = Math.max(
body.offsetHeight,
body.scrollHeight,
html.clientHeight,
html.offsetHeight,
html.scrollHeight
);

Element height

// jQuery
$el.height();

// Native
function getHeight(el) {
const styles = window.getComputedStyle(el);
const height = el.offsetHeight;
const borderTopWidth = parseFloat(styles.borderTopWidth);
const borderBottomWidth = parseFloat(styles.borderBottomWidth);
const paddingTop = parseFloat(styles.paddingTop);
const paddingBottom = parseFloat(styles.paddingBottom);
return height - borderBottomWidth - borderTopWidth - paddingTop - paddingBottom;
}

// accurate to integer（when `border-box`, it's `height - border`; when `content-box`, it's `height + padding`）
el.clientHeight;

// accurate to decimal（when `border-box`, it's `height`; when `content-box`, it's `height + padding + border`）
el.getBoundingClientRect().height;

2.3 Position & Offset

Position

Get the current coordinates of the element relative to the offset parent.

// jQuery
$el.position();

// Native
{ left: el.offsetLeft, top: el.offsetTop }

Offset

Get the current coordinates of the element relative to the document.

// jQuery
$el.offset();

// Native
function getOffset (el) {
const box = el.getBoundingClientRect();

return {
  top: box.top + window.pageYOffset - document.documentElement.clientTop,
  left: box.left + window.pageXOffset - document.documentElement.clientLeft
};
}

2.4 Scroll Top

Get the current vertical position of the scroll bar for the element.

// jQuery
$(window).scrollTop();

// Native
(document.documentElement && document.documentElement.scrollTop) || document.body.scrollTop;

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DOM Manipulation

3.1 Remove

Remove the element from the DOM.

// jQuery
$el.remove();

// Native
el.parentNode.removeChild(el);

3.2 Text
- Get text
  
  Get the combined text contents of the element including their descendants,
```
// jQuery
$el.text();

// Native
el.textContent;
```
- Set text
  
  Set the content of the element to the specified text.
```
// jQuery
$el.text(string);

// Native
el.textContent = string;
```

3.3 HTML

Get HTML

// jQuery
$el.html();

// Native
el.innerHTML;

Set HTML

// jQuery
$el.html(htmlString);

// Native
el.innerHTML = htmlString;

3.4 Append

Append child element after the last child of parent element

// jQuery: unified syntax for DOMString and Node objects
$parent.append(newEl | '<div id="container">Hello World</div>');

// Native: different syntax
parent.insertAdjacentHTML('beforeend', '<div id="container">Hello World</div>');
parent.appendChild(newEl);

// Native (ES6-way): unified syntax
parent.append(newEl | '<div id="container">Hello World</div>');

3.5 Prepend

// jQuery: unified syntax for DOMString and Node objects
$parent.prepend(newEl | '<div id="container">Hello World</div>');

// Native: different syntax
parent.insertAdjacentHTML('afterbegin', '<div id="container">Hello World</div>');
parent.insertBefore(newEl, parent.firstChild);

// Native (ES6-way): unified syntax
parent.prepend(newEl | '<div id="container">Hello World</div>');

3.6 insertBefore

Insert a new node before the selected elements

// jQuery
$newEl.insertBefore(selector);

// Native (HTML string)
el.insertAdjacentHTML('beforebegin ', '<div id="container">Hello World</div>');

// Native (Element)
const el = document.querySelector(selector);
if (el.parentNode) {
  el.parentNode.insertBefore(newEl, el);
}

3.7 insertAfter

Insert a new node after the selected elements

// jQuery
$newEl.insertAfter(selector);

// Native (HTML string)
el.insertAdjacentHTML('afterend', '<div id="container">Hello World</div>');

// Native (Element)
const el = document.querySelector(selector);
if (el.parentNode) {
  el.parentNode.insertBefore(newEl, el.nextSibling);
}

3.8 is

Return true if it matches the query selector

// jQuery - Notice `is` also works with a function, an existing jQuery object or a DOM element, which are not of concern here
$el.is(selector);

// Native
el.matches(selector);

3.9 clone

Create a deep copy of an element: it copies the matched element as well as all of its descendant elements and text nodes.

// jQuery. Sets parameter as `true` to indicate that event handlers should be copied along with the element.
$el.clone();

// Native
el.cloneNode();

3.10 empty

Remove all child nodes

// jQuery
$el.empty();

// Native
el.innerHTML = null;

3.11 wrap

Wrap an HTML structure around each element

// jQuery
$('.inner').wrap('<div class="wrapper"></div>');

// Native
Array.from(document.querySelectorAll('.inner')).forEach((el) => {
  const wrapper = document.createElement('div');
  wrapper.className = 'wrapper';
  el.parentNode.insertBefore(wrapper, el);
  wrapper.appendChild(el);
});

3.12 unwrap

Remove the parents of the set of matched elements from the DOM

// jQuery
$('.inner').unwrap();

// Native
Array.from(document.querySelectorAll('.inner')).forEach((el) => {
  let elParentNode = el.parentNode;

  if(elParentNode !== document.body) {
      elParentNode.parentNode.insertBefore(el, elParentNode);
      elParentNode.parentNode.removeChild(elParentNode);
  }
});

3.13 replaceWith

Replace each element in the set of matched elements with the provided new content

// jQuery
$('.inner').replaceWith('<div class="outer"></div>');

// Native (alternative) - latest, Edge17+
Array.from(document.querySelectorAll('.inner')).forEach((el) => {
  const outer = document.createElement('div');
  outer.className = 'outer';
  el.replaceWith(outer);
});

// Native
Array.from(document.querySelectorAll('.inner')).forEach((el) => {
  const outer = document.createElement('div');
  outer.className = 'outer';
  el.parentNode.replaceChild(outer, el);
});

3.14 simple parse

Parse a string into HTML/SVG/XML

// jQuery
$(`<ol>
  <li>a</li>
  <li>b</li>
</ol>
<ol>
  <li>c</li>
  <li>d</li>
</ol>`);

// Native
range = document.createRange();
parse = range.createContextualFragment.bind(range);

parse(`<ol>
  <li>a</li>
  <li>b</li>
</ol>
<ol>
  <li>c</li>
  <li>d</li>
</ol>`);

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Ajax

Fetch API is the new standard to replace XMLHttpRequest to do ajax. It works on Chrome and Firefox, you can use polyfills to make it work on legacy browsers.

Try github/fetch on IE9+ or fetch-ie8 on IE8+, fetch-jsonp to make JSONP requests.

4.1 Load data from the server and place the returned HTML into the matched element.

// jQuery
$(selector).load(url, completeCallback)

// Native
fetch(url).then(data => data.text()).then(data => {
  document.querySelector(selector).innerHTML = data
}).then(completeCallback)

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Events

For a complete replacement with namespace and delegation, refer to https://github.com/oneuijs/oui-dom-events

5.0 Document ready by DOMContentLoaded

  // jQuery
  $(document).ready(eventHandler);

  // Native
  // Check if the DOMContentLoaded has already been completed
  if (document.readyState !== 'loading') {
  eventHandler();
  } else {
  document.addEventListener('DOMContentLoaded', eventHandler);
  }

  // Native 
  // Example 2 - Ternary Operator - Async
  // Check if the DOMContentLoaded has already been completed
  (async function() {
  (document.readyState !== 'loading') ?
      eventHandler() : document.addEventListener('DOMContentLoaded',
        function() {
          eventHandler(); // EventHandler
        });
  })();

  // Native
  // Example 3 - Ternary Operator - Non Async
  // Check if the DOMContentLoaded has already been completed
  (function() {
  (document.readyState !== 'loading') ?
      eventHandler() : document.addEventListener('DOMContentLoaded',
        function() {
          eventHandler(); // EventHandler
        });
  })();

5.1 Bind an event with on

// jQuery
$el.on(eventName, eventHandler);

// Native
el.addEventListener(eventName, eventHandler);

5.2 Unbind an event with off

// jQuery
$el.off(eventName, eventHandler);

// Native
el.removeEventListener(eventName, eventHandler);

5.3 Trigger

// jQuery
$(el).trigger('custom-event', {key1: 'data'});

// Native
if (window.CustomEvent) {
  const event = new CustomEvent('custom-event', {detail: {key1: 'data'}});
} else {
  const event = document.createEvent('CustomEvent');
  event.initCustomEvent('custom-event', true, true, {key1: 'data'});
}

el.dispatchEvent(event);

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Utilities

Most of jQuery utilities are also found in the native API. Other advanced functions could be chosen from better utilities libraries, focusing on consistency and performance. Lodash is a recommended replacement.

6.1 Basic utilities

isArray

Determine whether the argument is an array.

// jQuery
$.isArray(array);

// Native
Array.isArray(array);

isWindow

Determine whether the argument is a window.

// jQuery
$.isWindow(obj);

// Native
function isWindow(obj) {
  return obj !== null && obj !== undefined && obj === obj.window;
}

inArray

Search for a specified value within an array and return its index (or -1 if not found).

// jQuery
$.inArray(item, array);

// Native
array.indexOf(item) > -1;

// ES6-way
array.includes(item);

isNumeric

Determine if the argument passed is numerical. Use typeof to decide the type or the type example for better accuracy.

// jQuery
$.isNumeric(item);

// Native
function isNumeric(n) {
  return !isNaN(parseFloat(n)) && isFinite(n);
}

isFunction

Determine if the argument passed is a JavaScript function object.

// jQuery
$.isFunction(item);

// Native
function isFunction(item) {
  if (typeof item === 'function') {
  return true;
  }
  var type = Object.prototype.toString.call(item);
  return type === '[object Function]' || type === '[object GeneratorFunction]';
}

isEmptyObject

Check to see if an object is empty (contains no enumerable properties).

// jQuery
$.isEmptyObject(obj);

// Native
function isEmptyObject(obj) {
  return Object.keys(obj).length === 0;
}

isPlainObject

Check to see if an object is a plain object (created using “{}” or “new Object”).

// jQuery
$.isPlainObject(obj);

// Native
function isPlainObject(obj) {
  if (typeof (obj) !== 'object' || obj.nodeType || obj !== null && obj !== undefined && obj === obj.window) {
  return false;
  }

  if (obj.constructor &&
      !Object.prototype.hasOwnProperty.call(obj.constructor.prototype, 'isPrototypeOf')) {
  return false;
  }

  return true;
}

extend

Merge the contents of two or more objects together into a new object, without modifying either argument. object.assign is part of ES6 API, and you could also use a polyfill.

// jQuery
$.extend({}, object1, object2);

// Native
Object.assign({}, object1, object2);

trim

Remove the white-space from the beginning and end of a string.

// jQuery
$.trim(string);

// Native
string.trim();

Translate all items in an array or object to new array of items.

// jQuery
$.map(array, (value, index) => {
});

// Native
array.map((value, index) => {
});

each

A generic iterator function, which can be used to seamlessly iterate over both objects and arrays.

// jQuery
$.each(array, (index, value) => {
});

// Native
array.forEach((value, index) => {
});

grep

Finds the elements of an array which satisfy a filter function.

// jQuery
$.grep(array, (value, index) => {
});

// Native
array.filter((value, index) => {
});

type

Determine the internal JavaScript [Class] of an object.

// jQuery
$.type(obj);

// Native
function type(item) {
  const reTypeOf = /(?:^\[object\s(.*?)\]$)/;
  return Object.prototype.toString.call(item)
  .replace(reTypeOf, '$1')
  .toLowerCase();
}

merge

Merge the contents of two arrays together into the first array.

// jQuery, doesn't remove duplicate items
$.merge(array1, array2);

// Native, doesn't remove duplicate items
function merge(...args) {
  return [].concat(...args)
}

// ES6-way, doesn't remove duplicate items
array1 = [...array1, ...array2]

// Set version, does remove duplicate items
function merge(...args) {
  return Array.from(new Set([].concat(...args)))
}

Return a number representing the current time.

// jQuery
$.now();

// Native
Date.now();

proxy

Takes a function and returns a new one that will always have a particular context.

// jQuery
$.proxy(fn, context);

// Native
fn.bind(context);

+ makeArray

Convert an array-like object into a true JavaScript array.

// jQuery
$.makeArray(arrayLike);

// Native
Array.prototype.slice.call(arrayLike);

// ES6-way: Array.from() method
Array.from(arrayLike);

// ES6-way: spread operator
[...arrayLike];

6.2 Contains

Check to see if a DOM element is a descendant of another DOM element.

// jQuery
$.contains(el, child);

// Native
el !== child && el.contains(child);

6.3 Globaleval

Execute some JavaScript code globally.

// jQuery
$.globaleval(code);

// Native
function Globaleval(code) {
  const script = document.createElement('script');
  script.text = code;

  document.head.appendChild(script).parentNode.removeChild(script);
}

// Use eval, but context of eval is current, context of $.Globaleval is global.
eval(code);

6.4 parse

parseHTML

Parses a string into an array of DOM nodes.

// jQuery
$.parseHTML(htmlString);

// Native
function parseHTML(string) {
  const context = document.implementation.createHTMLDocument();

  // Set the base href for the created document so any parsed elements with URLs
  // are based on the document's URL
  const base = context.createElement('base');
  base.href = document.location.href;
  context.head.appendChild(base);

  context.body.innerHTML = string;
  return context.body.children;
}

6.5 exists

exists

Check if an element exists in the DOM

// jQuery
if ($('selector').length) {
 // exists
}

// Native
var element =  document.getElementById('elementId');
if (typeof(element) != 'undefined' && element != null)
{
 // exists
}

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Promises

A promise represents the eventual result of an asynchronous operation. jQuery has its own way to handle promises. Native JavaScript implements a thin and minimal API to handle promises according to the Promises/A+ specification.

7.1 done, fail, always

done is called when promise is resolved, fail is called when promise is rejected, always is called when promise is either resolved or rejected.

// jQuery
$promise.done(doneCallback).fail(failCallback).always(alwaysCallback)

// Native
promise.then(doneCallback, failCallback).then(alwaysCallback, alwaysCallback)

7.2 when

when is used to handle multiple promises. It will resolve when all promises are resolved, and reject if either one is rejected.

// jQuery
$.when($promise1, $promise2).done((promise1Result, promise2Result) => {
});

// Native
Promise.all([$promise1, $promise2]).then([promise1Result, promise2Result] => {});

7.3 Deferred

Deferred is a way to create promises.

// jQuery
function asyncFunc() {
  const defer = new $.Deferred();
  setTimeout(() => {
  if(true) {
      defer.resolve('some_value_computed_asynchronously');
  } else {
      defer.reject('failed');
  }
  }, 1000);

  return defer.promise();
}

// Native
function asyncFunc() {
  return new Promise((resolve, reject) => {
  setTimeout(() => {
      if (true) {
        resolve('some_value_computed_asynchronously');
      } else {
        reject('failed');
      }
  }, 1000);
  });
}

// Deferred way
function defer() {
  const deferred = {};
  const promise = new Promise((resolve, reject) => {
  deferred.resolve = resolve;
  deferred.reject = reject;
  });

  deferred.promise = () => {
  return promise;
  };

  return deferred;
}

function asyncFunc() {
  const defer = defer();
  setTimeout(() => {
  if(true) {
      defer.resolve('some_value_computed_asynchronously');
  } else {
      defer.reject('failed');
  }
  }, 1000);

  return defer.promise();
}

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Animation

8.1 Show & Hide

// jQuery
$el.show();
$el.hide();

// Native
// More detail about show method, please refer to https://github.com/oneuijs/oui-dom-utils/blob/master/src/index.js#L363
el.style.display = ''|'inline'|'inline-block'|'inline-table'|'block';
el.style.display = 'none';

8.2 Toggle

Display or hide the element.

// jQuery
$el.toggle();

// Native
if (el.ownerDocument.defaultView.getComputedStyle(el, null).display === 'none') {
  el.style.display = ''|'inline'|'inline-block'|'inline-table'|'block';
} else {
  el.style.display = 'none';
}

8.3 FadeIn & FadeOut

// jQuery
$el.fadeIn(3000);
$el.fadeOut(3000);

// Native fadeOut
function fadeOut(el, ms) {
  if (ms) {
  el.style.transition = `opacity ${ms} ms`;
  el.addEventListener(
      'transitionend',
      function(event) {
        el.style.display = 'none';
      },
      false
  );
  }
  el.style.opacity = '0';
}

// Native fadeIn
function fadeIn(elem, ms) {
  elem.style.opacity = 0;

  if (ms) {
  let opacity = 0;
  const timer = setInterval(function() {
      opacity += 50 / ms;
      if (opacity >= 1) {
        clearInterval(timer);
        opacity = 1;
      }
      elem.style.opacity = opacity;
  }, 50);
  } else {
  elem.style.opacity = 1;
  }
}

8.4 FadeTo

Adjust the opacity of the element.

// jQuery
$el.fadeTo('slow',0.15);
// Native
el.style.transition = 'opacity 3s'; // assume 'slow' equals 3 seconds
el.style.opacity = '0.15';

8.5 FadeToggle

Display or hide the element by animating their opacity.

// jQuery
$el.fadeToggle();

// Native
el.style.transition = 'opacity 3s';
const { opacity } = el.ownerDocument.defaultView.getComputedStyle(el, null);
if (opacity === '1') {
  el.style.opacity = '0';
} else {
  el.style.opacity = '1';
}

8.6 SlideUp & SlideDown

// jQuery
$el.slideUp();
$el.slideDown();

// Native
const originHeight = '100px';
el.style.transition = 'height 3s';
// slideUp
el.style.height = '0px';
// slideDown
el.style.height = originHeight;

8.7 SlideToggle

Display or hide the element with a sliding motion.

// jQuery
$el.slideToggle();

// Native
const originHeight = '100px';
el.style.transition = 'height 3s';
const { height } = el.ownerDocument.defaultView.getComputedStyle(el, null);
if (parseInt(height, 10) === 0) {
  el.style.height = originHeight;
} else {
 el.style.height = '0px';
}

8.8 Animate

Perform a custom animation of a set of CSS properties.

// jQuery
$el.animate({ params }, speed);

// Native
el.style.transition = 'all ' + speed;
Object.keys(params).forEach((key) => {
  el.style[key] = params[key];
});

Alternatives

You Might Not Need jQuery - Examples of how to do common event, element, ajax etc with plain javascript.
npm-dom and webmodules - Organizations you can find individual DOM modules on NPM