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

23 May, 2019
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specifies the value to replace the search value with.Return value: It returns a new string where the defines value has been replaced by the new value.
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Return value: It returns a new string where the defines value has been replaced by the new value.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.
<!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>                    
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 $(dollar sign).
<!DOCTYPE HTML> <html>     <head>         <title>             Replace special characters with            _ (underscore)        </title>    </head>           <body style = "text-align:center;">               <h1 style = "color:green;" >             GeeksForGeeks         </h1>               <p id = "GFG_UP" style = "font-size: 16px; font-weight: bold;">        </p>                  <button onclick = "gfg_Run()">             Click here        </button>                  <p id = "GFG_DOWN" style =             "color:green; font-size: 20px; font-weight: bold;">        </p>                  <script>            var el_up = document.getElementById("GFG_UP");            var el_down = document.getElementById("GFG_DOWN");            var str = "A$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>                    
Output:
Before clicking on the button:
After clicking on the button:
JavaScript-Misc
JavaScript
Web Technologies
Web technologies Questions
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.