String indexOf()

In JavaScript, String.indexOf() method is used to find the index of the first occurrence of the search string in the string.

Syntax

str.indexOf(search, start)

• str is a string.
• search is a string.
• start is an integer, index position.

indexOf() method returns the index/position of the first occurrence of search string in the string str . If start is provided, the string str from the start position is considered for searching.

Examples

1. Find index of 'le' search string, in string variable name.

let name = 'apple';
let index = name.indexOf('le');
console.log(index);

2. Find index of 'an' search string in string variable name from a start position of 10.

let name = 'apple banana cherry banana mango';
let start = 10;
let index = name.indexOf('an', start);
console.log(index);

The first occurrence is ignored because the search happens from a start position of 10.

3. Find index of 'ba' search string in string variable name.

let name = 'apple';
let index = name.indexOf('ba');
console.log(index);

Since there is no occurrence of search string in the calling string, indexOf() returns -1.