How to count string occurrence in string using JavaScript?

In JavaScript, we can count the string occurrence in a string by counting the number of times the string present in the string. JavaScript provides a function match(), which is used to generate all the occurrences of a string in an array.
By counting the array size which will return the number of times the sub-string present in a string.
Script to find the number of occurrences in a string:

  • Example-1: Counting occurrence of Geeks in “GeeksforGeeks” using “match()” function.
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    <!DOCTYPE html>
    <html>
      
    <head>
        <title>
            count string occurrence in a string
        </title>
    </head>
      
    <body style="text-align:center;">
      
        <h1 style="color:green;"
            GeeksForGeeks 
        </h1>
        <h3>
          count string occurrence in a string 
      </h3>
      
        <button onClick="gfg()">
            count
        </button>
        <p id="rk">
      
        </p>
      
        <!-- Script to count string 
             occurrence in a string  -->
        <script>
            function gfg() {
                var r = "Geeks For Geeks ";
                document.getElementById("rk").innerHTML =
                  (r.match(/Geeks/g)).length;
      
            }
        </script>
    </body>
      
    </html>

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    Output:

    • Before clicking on the Button:


    • After clicking on the Button:

    The ‘g’ in the function specifies global which is used to search for an entire string rather than stop by finding the first occurrence.

  • Another Example to count the number of times the string appears in a string.
    Example-2: Counting occurrence of for in “GeeksforGeeks” using Loops.

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    <!DOCTYPE html>
    <html>
      
    <head>
        <title>
            count string occurrence in a string
        </title>
    </head>
      
    <body style="text-align:center;">
      
        <h1 style="color:green;"
            GeeksForGeeks 
        </h1>
        <h3>
          count string occurrence in a string 
      </h3>
      
        <button onClick="gfg()">
            count
        </button>
        <p id="rk">
      
        </p>
      
        <!-- Script to count 
            string occurrence in a string  -->
        <script>
            function gfg() {
                var s = "Geeks for Geeks";
                var f = "for";
                var i = 0,
                    n = 0,
                    j = 0;
      
                while (true) {
                    j = s.indexOf(f, j);
                    if (j >= 0) {
                        n++;
                        j++;
                    } else
                        break;
                }
                document.getElementById(
                  "rk").innerHTML = n;
            }
        </script>
    </body>
      
    </html>

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    Output:

    • Before clicking on the Button :
    • After clicking on the Button:

  • Example-3: Counting occurrence of Geeks in “GeeksforGeeks” using split function.
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    <!DOCTYPE html>
    <html>
      
    <head>
        <title>
            count string occurrence in a string
        </title>
    </head>
      
    <body style="text-align:center;">
      
        <h1 style="color:green;"
            GeeksForGeeks 
        </h1>
        <h3>
          count string occurrence in a string 
      </h3>
      
        <button onClick="gfg()">
            count
        </button>
        <p id="rk">
      
        </p>
      
        <!-- Script to count string 
             occurrence in a string  -->
        <script>
            function gfg() {
                var s = "Geeks for Geeks";
                var f = "Geeks";
                var r = s.split(f).length - 1;
                document.getElementById("rk").innerHTML = r;
            }
        </script>
    </body>
      
    </html>

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    Output:

    • Before clicking on the Button:
    • After clicking on the Button:

  • Example-4:Counting occurrence of Geeks in “GeeksforGeeks” using indexof().
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    <!DOCTYPE html>
    <html>
      
    <head>
        <title>
            count string occurrence in a string
        </title>
    </head>
      
    <body style="text-align:center;">
      
        <h1 style="color:green;"
            GeeksForGeeks 
        </h1>
        <h3>
          count string occurrence in a string
      </h3>
      
        <button onClick="gfg()">
            count
        </button>
        <p id="rk">
      
        </p>
      
        <!-- Script to count 
             string occurrence in a string  -->
        <script>
            function gfg() {
                var s = "Geeks for Geeks";
                var f = "Geeks";
                var r = s.indexOf(f);
                var c = 0;
                while (r != -1) {
                    c++;
                    r = s.indexOf(f, r + 1);
                }
                document.getElementById("rk").innerHTML = c;
            }
        </script>
    </body>
      
    </html>

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    Output:

    • Before clicking on the Button :
    • After clicking on the Button:



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