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

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.

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<!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>                    

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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.











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<!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>                     



















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Output:


    

  • 
Before clicking on the button:
    


    • 

  • 
After clicking on the button:
    


    • 



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