💭 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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