Mezbaul Abedin Forhan
3 min readNov 2, 2020


Top 10 Most Used Javascript Strings and Numbers methods:

Javascript is a hot programming language now. As a beginner, we should learn javascript in an effective way. A well-understood javascript programmer needs time for understanding all the methods and master them. But as a beginner, you will need these a lot

Strings: Strings are useful for holding data that can be represented in text form. It is widely used in our daily life.

How to create a string in javascript??

It’s so simple just declare a variable and assign value to it. You can use let, const, var before declaring a variable

console.log(txt) // output:"ABCDEFGHIJKLMNOPQRSTUVWXYZ";

Another way to declare string with string() method: Javascript treats it’s like an object.

const stringAsObject= new String("A String as an object");
console.log(typeof(stringAsObject)); //object

Length: The length property returns the length of a string:

var str= "I am a string";
var strLength= txt.length;
console.log(strLength) // output: 13//
// length count counts extra space//

indexOf(): It is used to find a specific string in a string

const  str = "Please locate where 'beautiful' word lies!";
const pos = str.indexOf("beautiful"); //Output: 7 //


slice() extracts a part of a string and returns the extracted part in a new string.

The method takes 2 parameters: the start position, and the end position (end not included).

const str = "Car, Boat, Bike";
var res= str.slice(7, 11); //Output:Boat //

substring(positive start,positive end) :

substring() is similar to slice().

The difference is that substring() cannot accept negative indexes.

const str = "Car, Boat, Bike";
var res= str.substring(7, 11); //Output:Boat //

substr(start,extract length):

substr() is similar to slice().

The difference is that the second parameter specifies the length of the extracted part.

const str = "Car, Boat, Bike";
var res= str.substring(7, 10); //Output:Boa //

Let’s talk about Numbers.

JavaScript has only one type of number. Numbers can be written with or without decimals.

How to declare a numbers?

const  x = 3.14;    // A number with decimals
const y = 3; // A number without decimals

Extra large or extra small numbers can be written with scientific (exponent) notation

const x = 123e5;    // 12300000
const y = 123e-5; // 0.00123


The tostring() method returns a number as a string.

All number methods can be used on any type of numbers (literals, variables, or expressions) :

const  num= 123;
x.toString(); // returns 123 from variable num
(123).toString(); // returns 123 from literal 123
(100 + 23).toString(); // returns 123 from expression 100 + 23


toFixed() returns a string, with the number written with a specified number of decimals:

const x = 9.656;
x.toFixed(0); // returns 10
x.toFixed(2); // returns 9.66
x.toFixed(4); // returns 9.6560
x.toFixed(6); // returns 9.656000


Number() can be used to convert JavaScript variables to numbers:

Number(true);          // returns 1
Number(false); // returns 0
Number("10"); // returns 10
Number(" 10"); // returns 10
Number("10 "); // returns 10
Number(" 10 "); // returns 10
Number("10.33"); // returns 10.33
Number("10,33"); // returns NaN
Number("10 33"); // returns NaN
Number("John"); // returns NaN


parseInt() parses a string and returns a whole number. Spaces are allowed. Only the first number is returned:

parseInt("10");         // returns 10
parseInt("10.33"); // returns 10
parseInt("10 20 30"); // returns 10
parseInt("10 years"); // returns 10
parseInt("years 10"); // returns NaN


parseFloat() parses a string and returns a number. Spaces are allowed. Only the first number is returned:

parseFloat("10");        // returns 10
parseFloat("10.33"); // returns 10.33
parseFloat("10 20 30"); // returns 10
parseFloat("10 years"); // returns 10
parseFloat("years 10"); // returns NaN