10 useful JavaScript method every JavaScript developer should know

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As a JavaScript developer, You should know these JavaScript methods.

1.parseInt(): This method converts a string to an integer.

Example:

var num = ‘11’;
console.log(typeof num); //string
num = parseInt(num);
console.log(typeof num); //number

2.includes(): This method returns true or false. If a string or array contains the characters of a specified string or contains a specified element of an array, then this method returns true, and if not, then returns false.

Example:

var name = [“Limon”, “Mahbub”, “Alam”, “Tanvir”];
var isInclude = name.includes(“Alam”);
console.log(isInclude); // true

3.map(): This method creates a new array by calling a function. This function will then be executed on each of the array’s elements.

Example:

const numbers = [2, 4, 6, 8];
const numbersMap = numbers.map(num => num * 2);
console.log(numbersMap); //4, 8, 12, 16

4. forEach(): This method used to loop through an array by passes a callback function.

Example:

const fruits = [“Banana”, “Mango”, “Orange”, “Apple”, “Dragon Fruit”];
fruits.forEach(fruit => console.log(fruit));
/*
Output:
Banana
Mango
Orange
Apple
Dragon Fruit
*/

5. concat(): This method joins multiple arrays by returning a new array

Example:

const num1 = [1,2,3];
const num2 = [4,5,6];
const num3 = num1.concat(num2);
console.log(num3); //1, 2, 3, 4, 5, 6

6.join(): This method converts an array to a string by concatenating all of the array’s elements separated by the specified separator.

Example:

const nameElements = [“L”,”i”,”m”,”o”,”n”];
console.log(nameElements.join(‘’));//Limon

7.substr(): This method returns a string. This string stating with a specific index, ending with a specific length.

Example:
const nameStr = ‘Mahbubul’;
console.log(nameStr.substr(3, 6)); //bubul

7.toUppercase(): This method converts a string value to uppercase.

Example:

const subject = ‘Computer Science and Engineering’;
console.log(subject.toUpperCase()); //COMPUTER SCIENCE AND ENGINEERING

8.Math.random(): This method returns a random floating-point value.

Example:

const randomNumber = Math.random();
console.log(randomNumber); //generate floating-point random number between 0 to 1

9.Math.round(): This method returns a round number to the closest integer.

Example:

console.log(Math.round(4.42)); //4

10.splice (): This method created a new array by removing or replacing existing array elements.

Example:

const nums = [1,2,4,5,6];
nums.splice(2, 0, 3);
console.log(nums); //1, 2, 3, 4, 5, 6