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December 1, 2021 05:42 am GMT

Javascript snippets you need to know right now - 4

Hello my fellow readers!
If you have really come this far in this series of posts, I would like to thank you for your support in reading all of the posts in this series. Thank you and do follow me on Twitter for more tech content soon. Let's get started.

1 Drop Elements
This snippet returns a new array with n elements removed from the left.

const drop = (arr, n = 1) => arr.slice(n);drop([1, 2, 3]); // [2,3]drop([1, 2, 3], 2); // [3]drop([1, 2, 3], 42); // []

2 dropRight
This snippet returns a new array with n elements removed from the right.

const dropRight = (arr, n = 1) => arr.slice(0, -n);dropRight([1, 2, 3]); // [1,2]dropRight([1, 2, 3], 2); // [1]dropRight([1, 2, 3], 42); // []

3 dropRightWhile
This snippet removes elements from the right side of an array until the passed function returns true.

const dropRightWhile = (arr, func) => {  while (arr.length > 0 && !func(arr[arr.length - 1])) arr = arr.slice(0, -1);  return arr;};dropRightWhile([1, 2, 3, 4], n => n < 3); // [1, 2]

4 dropWhile
This snippet removes elements from an array until the passed function returns true.

const dropWhile = (arr, func) => {  while (arr.length > 0 && !func(arr[0])) arr = arr.slice(1);  return arr;};dropWhile([1, 2, 3, 4], n => n >= 3); // [3,4]

5 elementContains
This snippet checks whether the parent element contains the child.

const elementContains = (parent, child) => parent !== child && parent.contains(child);elementContains(document.querySelector('head'), document.querySelector('title')); // trueelementContains(document.querySelector('body'), document.querySelector('body')); // false

6 Filter Duplicate Elements
This snippet removes duplicate values in an array.

const filterNonUnique = arr => arr.filter(i => arr.indexOf(i) === arr.lastIndexOf(i));filterNonUnique([1, 2, 2, 3, 4, 4, 5]); // [1, 3, 5]

7 findKey
This snippet returns the first key that satisfies a given function.

const findKey = (obj, fn) => Object.keys(obj).find(key => fn(obj[key], key, obj));findKey(  {    barney: { age: 36, active: true },    fred: { age: 40, active: false },    pebbles: { age: 1, active: true }  },  o => o['active']); // 'barney'

8 findLast
This snippet returns the last element for which a given function returns a truthy value.

const findLast = (arr, fn) => arr.filter(fn).pop();findLast([1, 2, 3, 4], n => n % 2 === 1); // 3

9 insertAfter
This snippet can be used to insert an HTML string after the end of a particular element.

const insertAfter = (el, htmlString) => el.insertAdjacentHTML('afterend', htmlString);insertAfter(document.getElementById('myId'), '<p>after</p>'); // <div id="myId">...</div> <p>after</p>

insertBefore
This snippet can be used to insert an HTML string before a particular element.

const insertBefore = (el, htmlString) => el.insertAdjacentHTML('beforebegin', htmlString);insertBefore(document.getElementById('myId'), '<p>before</p>'); // <p>before</p> <div id="myId">...</div>

Thank you for reading!

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Until next time,
Abhiraj

Original Link: https://dev.to/abhirajb/javascript-snippets-you-need-to-know-right-now-4-3a2l

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