Replace special characters in a string with underscore (_) in JavaScript

JavaScript replace() method is used to replace all special characters from a string with _ (underscore) which is described below:

  • replace() method: This method searches a string for a defined value, or a regular expression, and returns a new string with the replaced defined value.

    Syntax:

    string.replace(searchVal, newvalue)

    Parameters:

    • searchVal: It is required parameter. It specifies the value, or regular expression, that is going to replace by the new value.
    • newvalue: It is required parameter. It specifies the value to replace the search value with.

    Return value: It returns a new string where the defines value has been replaced by the new value.

Example 1: This example replaces all special characters with _ (underscore) using replace() method.

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<!DOCTYPE HTML> 
<html> 
    <head> 
        <title> 
            Replace special characters in a
            string with _ (underscore)
        </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 = "This, is# GeeksForGeeks!";
            el_up.innerHTML = str;
              
            function gfg_Run() {
                el_down.innerHTML = 
                    str.replace(/[&\/\\#, +()$~%.'":*?<>{}]/g, '_');
            }         
        </script> 
    </body> 
</html>                    

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Output:


    

  • 
Before clicking on the button:
    


    • 

  • 
After clicking on the button:
    


    • 



Example 2:  This example replace a unique special character with _ (underscore). This example goes to each character and checks if it is a special character that we are looking for, then it will replace the character. In this example the unique character is $(dollar sign).











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<!DOCTYPE HTML>  


<html>  


    <head>  


        <title>  


            Replace special characters with 


            _ (underscore) 


        </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 = "A$computer$science$portal$for$Geeks"; 


            el_up.innerHTML = str; 


              


            function gfg_Run() { 


                  


                var newStr = ""; 


                  


                for(var i=0; i<str.length; i++) {  


                    if (str[i] == '$') { 


                        newStr += '_'; 


                    } 


                    else { 


                        newStr += str[i]; 


                    } 


                } 


                el_down.innerHTML = newStr; 


            }          


        </script>  


    </body>  


</html>                     



















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Output:


    

  • 
Before clicking on the button:
    


    • 

  • 
After clicking on the button:
    


    • 




          
          
          
          

            

    

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