Javascript String substring()

 const message = "JavaScript is fun."; 
// get the substring starting from index 0 to 10 let result = message.substring(0, 10);
 console.log(result); // Output: JavaScript

substring() Syntax

The syntax of the substring() method is:

 str.substring(indexStart, indexEnd)

Here, str is a string.

substring() Parameters

The substring() method takes in:

• indexStart - The index of the first character to start including in the returned substring.
• indexEnd (optional) - The index before which to stop extraction. (Exclusive) If omitted, it extracts till the end of the string.

substring() Return Value

• Returns a new string containing the specified part of the given string.

Note: substring() does not change the original string.

Example 1: Using substring

 let string = "Programiz JavaScript Tutorials"; 
// first character substr1 = string.substring(0, 1);
 console.log(substr1); // P 
// if start > end, they are swapped substr2 = string.substring(1, 0);
 console.log(substr2); // P // From 11th to last character substr3 = string.substring(10); console.log(substr3); // JavaScript Tutorials // the extreme values are 0 and str.length 
// same as string.substring(0) substr4 = string.substring(-44, 90);
 console.log(substr4); // Programiz JavaScript Tutorials 
// indexEnd is exclusive substr5 = string.substring(0, string.length - 1);
 console.log(substr5); // Programiz JavaScript Tutorial

Output

 P P JavaScript Tutorials Programiz JavaScript Tutorials Programiz JavaScript Tutorial

Example 2: Replacing a substring within a string

 // Replaces old characters with new characters in a string function replaceString(oldChars, newChars, string) { for (let i = 0; i < string.length; ++i) { 
 if (string.substring(i, i + oldChars.length) == oldChars) { string = string.substring(0, i) + newChars + string.substring(i + oldChars.length, string.length);
 } } return string; } const string = "Java Tutorials"; let newString = replaceString("Java", "JavaScript", string); console.log(newString); // JavaScript Tutorials

Output

 JavaScript Tutorials

Also Read:

• JavaScript String slice()