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    Return value: It returns a new string where the defines value has been replaced by the new value.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

filter_none

edit
close

play_arrow

link
brightness_4
code

<!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>                    

chevron_right


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).

filter_none

edit
close

play_arrow

link
brightness_4
code

<!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>                    

chevron_right


Output:

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


My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.