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How to check a string is entirely made up of the same substring in JavaScript ?

  • Last Updated : 10 Jun, 2019

Given a string and the task is to determine whether the string is made up of the same substrings or not.

Approach:

  • Initialize a string to the variable.
  • Use test() method to test a pattern in a string.
  • The test() method returns true if match is found, otherwise it returns false.

Example 1: This example checks for string geeksgeeksgeeks which is made up of same substring, so it returns True.




<!DOCTYPE HTML> 
<html
    <head
        <title
            How to check a string is entirely
            made of same substring ?
        </title>
    </head
      
    <body style = "text-align:center;"
  
        <h1 style = "color:green;"
            GeeksForGeeks 
        </h1
  
        <p id = "GFG_UP" style =
            "font-size: 16px; font-weight: bold;">     
        </p>
          
        <button onclick = "gfg_Run()"
            Click here
        </button>
          
        <p id = "GFG_DOWN" style =
            "color:green; font-size: 20px; font-weight: bold;">
        </p>
          
        <script>
            var el_up = document.getElementById("GFG_UP");
            var el_down = document.getElementById("GFG_DOWN");
          
            var str = "geeksgeeksgeeks";
          
            el_up.innerHTML = "Str = '" + str + "'";
            function check(str) {
                return /^(.+)\1+$/.test(str)
            }
              
            function gfg_Run() {
                ans = "String is not made up of same substrings";
                if (check(str)) {
                    ans = "String is made up of same substrings"; 
                }
                el_down.innerHTML = ans;
            }         
        </script
    </body
</html>                    

Output:

  • Before clicking on the button:
  • After clicking on the button:

Example 2: This example checks for string geeksgeekgeeks which is not made up of same substrings so it returns False.




<!DOCTYPE HTML> 
<html
    <head
        <title
            How to check a string is entirely
            made of same substring ?
        </title>
    </head
      
    <body style = "text-align:center;"
  
        <h1 style = "color:green;"
            GeeksForGeeks 
        </h1
  
        <p id = "GFG_UP" style =
            "font-size: 16px; font-weight: bold;">     
        </p>
          
        <button onclick = "gfg_Run()"
            Click here
        </button>
          
        <p id = "GFG_DOWN" style =
            "color:green; font-size: 20px; font-weight: bold;">
        </p>
          
        <script>
            var el_up = document.getElementById("GFG_UP");
            var el_down = document.getElementById("GFG_DOWN");
          
            var str = "geeksgeekgeeks";
          
            el_up.innerHTML = "Str = '" + str + "'";
            function check(str) {
                return /^(.+)\1+$/.test(str)
            }
              
            function gfg_Run() {
                ans = "String is not made up of same substrings";
                if (check(str)) {
                    ans = "String is made up of same substrings"; 
                }
                el_down.innerHTML = ans;
            }         
        </script
    </body
</html>                    

Output:

  • Before clicking on the button:
  • After clicking on the button:

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