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JavaScript | RegExp \b Metacharacter
  • Last Updated : 22 Apr, 2019

The RegExp \b Metacharacter in JavaScript is used to find a match at the beginning or end of a word. If match is found it returns the word else it returns NULL.

Syntax:

/\b/ 

or

new RegExp("\\b")

Syntax with modifiers:

/\b/g 

or



new RegExp("\\b", "g")

Example 1: This example matches the word “GeeksforGeeks” at the beginning of the string.

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<!DOCTYPE html>
<html>
  
<head>
    <title>
        JavaScript RegExp \b Metacharacter
    </title>
</head>
  
<body style="text-align:center">
      
    <h1 style="color:green">
        GeeksforGeeks
    </h1>
      
    <h2>RegExp \b Metacharacter</h2>
      
    <p>Input String: GeeksforGeeks@_123_$</p>
      
    <button onclick="geek()">
        Click it!
    </button>
      
    <p id="app"></p>
      
    <script>
        function geek() {
            var str1 = "GeeksforGeeks@_123_$";
            var regex4 = /\bgeeksforgeeks/gi;
            var match4 = str1.match(regex4);
  
            document.getElementById("app").innerHTML = 
                    "Found " + match4.length
                    + " match: " + match4;
        }
    </script>
</body>
  
</html>                    

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Output:
Before Clicking the button:
backd
After Clicking the button:
backd

Example 2: This example matches the word “Geeky” at the beginning and replaces it with the word “GFG”.

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<!DOCTYPE html>
<html>
  
<head>
    <title>
        JavaScript RegExp \b Metacharacter
    </title>
</head>
  
<body style="text-align:center">
      
    <h1 style="color:green">
        GeeksforGeeks
    </h1>
      
    <h2>RegExp \b Metacharacter</h2>
      
    <p>String: Geeky@128</p>
      
    <button onclick="geek()">
        Click it!
    </button>
      
    <p id="app"></p>
      
    <script>
        function geek() {
            var str1 = "Geeky@128"; 
            var regex4 = new RegExp("\\bGeeky", "gi");         
            var replace = "GFG";
            var match4 = str1.replace(regex4, replace);
            document.getElementById("app").innerHTML = 
                " New string: " + match4;
        }
    </script>
</body>
  
</html>                    

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Output:
Before Clicking the button:
backd
After Clicking the button:
backd

Supported Browsers: The browsers supported by RegExp \b Metacharacter are listed below:

  • Google Chrome
  • Apple Safari
  • Mozilla Firefox
  • Opera
  • Internet Explorer

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