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JavaScript | RegExp \B Metacharacter

  • Last Updated : 22 Apr, 2019
Geek Week

The RegExp \B Metacharacter in JavaScript is used to find a match which is not present at the beginning or end of a word. If a 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 “for” which is not present at the beginning or end of the word.




<!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 = /\Bfor/gi;
            var match4 = str1.match(regex4);
  
            document.getElementById("app").innerHTML = 
                    "Found " + match4.length
                    + " match: " + match4;
        }
    </script>
</body>
  
</html>                    

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

Example 2: This example match the word “Geeky” and replaces it with “GEEKY”.




<!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: 123geeky456</p>
      
    <button onclick="geek()">
        Click it!
    </button>
      
    <p id="app"></p>
      
    <script>
        function geek() {
        var str1 = "123geeky456";
            var regex4 = new RegExp("\\Bgeeky", "gi");         
            var replace = "GEEKY";
            var match4 = str1.replace(regex4, replace);
            document.getElementById("app").innerHTML = 
                    " New string: " + match4;
        }
    </script>
</body>
  
</html>                    

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

Hey geek! The constant emerging technologies in the world of web development always keeps the excitement for this subject through the roof. But before you tackle the big projects, we suggest you start by learning the basics. Kickstart your web development journey by learning JS concepts with our JavaScript Course. Now at it’s lowest price ever!




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