How to get nth occurrence of a string in JavaScript ?

In this article, the task is to get the nth occurrence of a substring in a string with the help of JavaScript. We have many methods to do this some of which are described below:

Approaches to get the nth occurrence of a string:

• Using split() and join() methods
• Using indexOf() method

Approach 1: Using split() and join() methods

• First, split the string into sub-strings using the split() method by passing the index also.
• Again join the substrings on the passed substring using join() method.
• Returns the index of the nth occurrence of the string.

Example: In this example, the split() and join() methods are used to get the index of a substring. 

Javascript

// Input string
let string = "Geeks gfg Geeks Geek Geeks gfg";

// String to search
let searchString = "Geeks";

// occurrence number
let occurrence = 3;
console.log(
    occurrence +
        "rd occurrence of a '" +
        searchString +
        "' in " +
        string +
        "'."
);

// Function to get index of occurrence
function getPos(str, subStr, i) {
    return str.split(subStr, i).join(subStr).length;
}

function GFG_Fun() {
    console.log(getPos(
        string,
        searchString,
        occurrence
    ));
}

GFG_Fun();

Output

3rd occurrence of a 'Geeks' in Geeks gfg Geeks Geek Geeks gfg'.
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Approach 2: Using indexOf() method

Go through each substring one by one and return the index of the last substring. This approach uses the indexOf() method to return the index of the n^th occurrence of the string. 

Example: This example uses the indexOf() method to find the index of a substring.

Javascript

// Input string
let string = "Geeks gfg Geeks Geek Geeks gfg";

// String to search
let searchString = "Geeks";

// occurrence number
let occurrence = 3;
console.log(
    occurrence +
        "rd occurrence of a '" +
        searchString +
        "' in " +
        string +
        "'."
);

// Function to get index of occurrence
function getIndex(str, substr, ind) {
    let Len = str.length,
        i = -1;
    while (ind-- && i++ < Len) {
        i = str.indexOf(substr, i);
        if (i < 0) break;
    }
    return i;
}

function GFG_Fun() {
    console.log(getIndex(string, searchString, occurrence));
}

GFG_Fun();

Output

3rd occurrence of a 'Geeks' in Geeks gfg Geeks Geek Geeks gfg'.
21