25 powerful methods in JavaScript

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Why this thread?

⬘ Are you learning JavaScript? Even if you are experienced, do you ever feel exhausted by the presence of so many methods?

⬙ The best approach to getting familiar is to know the use cases for these.

Here are 25 methods. Let's discuss their use cases.

The methods are,

➤ Array.prototype's

➊ forEach()
➋ map()
➌ reduce()
➍ every()
➎ filter()
➏ find()
➐ slice()
➑ splice()
➒ push()
➓ pop()
➊➊ shift()
➊➋ unshift()
➊➌ indexOf()
➊➍ findIndex()
➊➎ sort()

➤ String.prototype's

➊➏ toLowerCase()
➊➐ toUpperCase()
➊➑ substring()
➊➒ indexOf()
20. charAt()
➋➊ trim()

➤ Math's

➋➋ floor()
➋➌ random()

➤ Global Methods

➋➍ setTimeout()
➋➎ setInterval()

➊ Array.prototype.forEach()

➤ Use Case

To iterate through each element in the array

Perform a task on each element

✘ Not suitable if the task is supposed to return some value

✩✩ forEach() is also available in Set.prototype and Map.prototype

➋ Array.prototype. map()

➤ Use Case

To iterate through each element in the array

Perform a task on each element which returns a value

Returns a new array with all returned values

✘ Not suitable if the task doesn't return any value

➌ Array.prototype.reduce()

➤ Use Case

To iterate through each element in the array

Perform a task on each element which accumulates the previous returned value with current element to return a new value

➤ Example

➀ Sum of all items
➁ Max of all items

➍ Array.prototype.every()

➤ Use Case

To iterate through elements in the array until a certain condition is not met

The task performed on each element must return a boolean value

✘ Stops iterating when condition is not met. Hence, it's not suitable for skipping.

➎ Array.prototype.filter()
➏ Array.prototype.find()

➤ Use Case

To find element(s) which match a criteria

Use find() to find the first matched element

Use filter() to find all matched elements

✩✩ filter() returns a new array of matched elements

➐ Array.prototype.slice()

➤ Use Case

To fetch a sub-array from a larger array

✩✩ slice() returns a new array, doesn't modify the existing array

➑ Array.prototype.splice()

➤ Use Case

To replace a portion of the array with new elements

✩✩ splice() modifies the existing array

Array.prototype's
➒ push()
➓ pop()
➊➊ shift()
➊➋ unshift()

➤ Use Case

Use push() and pop() to insert/remove elements from the end.

Use shift() and unshift() to insert/remove elements from the start.

✩✩ These methods modify the existing array

Array.prototype's
➊➌ indexOf()
➊➍ findIndex()

➤ Use Case

To find the index of the first matched element

indexOf() does exact match (===)

findIndex() allows for custom match

➊➎ Array.prototype.sort()

➤ Use Case

To sort all elements of an array in some order

Provide a comparator to define custom order

By default sorting order is lexical

✩✩ This method modifies the existing array

String.prototype's
➊➏ toLowerCase()
➊➐ toUpperCase()

➤ Use Case

To convert entire string to lowercase alphabets, use toLowerCase()

To convert entire string to uppercase alphabets, use toLowerCase()

✩✩ These methods returns a new string

➊➑ String.prototype.substring()

➤ Use Case

To fetch a part of the string between 2 indexes

✩✩ substring() returns a new string

➊➒ String.prototype.indexOf()

➤ Use Case

To find the very first occurrence of a "substring" in the original string

We can also mention from which index the occurrence should be checked

20. String.prototype.charAt()

➤ Use Case

To fetch the character at a specific position of a string.

The character fetched is in UTF-16 and returned as a string.

➋➊ String.prototype.trim()

➤ Use Case

To remove whitespace from both ends of a string

✩✩ trim() returns a new string

➋➋ Math.floor()

➤ Use Case

To get the largest integer less than or, equals to the given number

➋➌ Math.random()

➤ Use Case

To get a floating-point pseudo-random number in the range of 0 to less than 1

It can be multiplied by any number to make a random number being generated in the range of 0 to less than that number

➋➍ setTimeout()

➤ Use Case

To execute a function or, piece of code after a timer expires

The code is executed only once.

✘ It is an asynchronous function. It shouldn't be used where pausing of execution is intended.

➋➎ setInterval()

➤ Use Case

To execute a function or, piece of code repeatedly with a fix time delay

✘ The code is ensured to be executed each time after the time delay. But not "exactly" after the time delay.

✩✩ Cancel further execution using clearInterval()

Tasks for you

Find use cases of below

➤ String.prototypes's
❍ startsWith() / endsWith()
❍ fromCharCode()
❍ padStart() / padEnd()
❍ repeat()
❍ match() / matchAll()
❍ replace() / replaceAll()

➤ Math's
❍ ceil()
❍ trunc()
❍ round()

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