JavaScript Code

JavaScript String indexOf()


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.


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