JavaScript String indexOf() Method
The JavaScript String indexOf() method finds the index of the first occurrence of the argument string in the given string. The value returned is 0-based.
The
indexOf()method is case sensitive.
Syntax:
str.indexOf(searchValue , index);Parameters:
- searchValue: The searchValue is the string that is to be searched in the base string.
- index: The index defines the starting index from where the search value is to be searched in the base string.
Return value:
The first position is where the search value occurs. -1 if it never occurs.
Example 1: Below is an example of the String indexOf() Method.
JavaScript
function func() { // Original string let str = 'Departed Train'; // Finding index of occurrence of 'Train' let index = str.indexOf('Train'); console.log(index);}func(); |
Output
9
Example 2: In this example, the indexOf() method finds the index of the string ed Tr. Since the first and only index where this string is present is 6, therefore this function returns 6 as the answer.
JavaScript
// JavaScript to illustrate indexOf() methodfunction func() { // Original string let str = 'Departed Train'; // Finding index of occurrence of 'Train' let index = str.indexOf('ed Tr'); console.log(index);}func(); |
Output
6
Example 3: In this example, the indexOf() method finds the index of the string Train. Since the searchValue is not present in the string, therefore this function returns -1 as the answer.
JavaScript
function func() { // Original string let str = 'Departed Train'; // Finding index of occurrence of 'Train' let index = str.indexOf('train'); console.log(index);}func(); |
Output
-1
Example 4: In this example, the indexOf() method finds the index of the string Train. Since the first index of the searchValue is 9, therefore this function returns 9 as the answer.
JavaScript
function func() { // Original string let str = 'Departed Train before another Train'; // Finding index of occurrence of 'Train' let index = str.indexOf('Train'); console.log(index);}func(); |
Output
9
We have a complete list of Javascript string methods, to check those please go through this Javascript String Complete reference article.
Supported browser:
- Chrome 1 and above
- Edge 12 and above
- Firefox 1 and above
- Internet Explorer 3 and above
- Opera 3 and above
- Safari 1 and above
