Swapna Kumar Panda

Swapna Kumar Panda

13-06-2022

12:20

25 powerful methods in JavaScript ⇩

💭 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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