JavaScript replace regex use | Example code

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JavaScript replace() function has limitation. Simple characters can easily be replaced but What if we’re concerned with a pattern instead? The replace() method used with RegEx can achieve this.

Example replace with regex in JavaScript

Simple example code use RegEx, the first argument of replace will be replaced with regex syntax, for example /regex/.

The .replace() returns a new string, and the original remains the same. The .replace() will only replace the first matched pattern it finds unless use regex with the g flag to replace all matches.

<!doctype html>
  <head>

    <script>
      const str = '1 paidCodeCamp paid';
      const res1 = str.replace('paid', 'free');
      const res2 = str.replace(/paid/g, 'free');


      console.log(res1);
      console.log(res2);

    </script>
  </head>
  <body>

  </body>
  </html>

Output:

JavaScript replace regex use

Replace special characters from a string

let str = "Javascript123  #* Is The &^  Most Popular  Language";
      var res = str.replace(/[`[email protected]#$%^&*()_|+\-=?;:'",.<>\{\}\[\]\\\/]/gi, '');
      console.log(res);

Output:

Javascript123   Is The   Most Popular  Language

Replace spaces from a string

dummyString.replace(/\s+/g, '');

Replace anything but digits from a string

dummyString.replace(/[^0-9]/g,'');

Understand:

  • /and / marks the beginning and end of a pattern
  • [^0-9] matches all characters except digits within the string.
  • g specifies to match all occurrences of the pattern within the string.
  • \s+ matches at least one space character within the string.
  • [ ] finds the characters within the brackets
  • `[email protected]#$%^&*()_|+-=?;:’”,.<>{}[]\\/ matches these special characters within the string

Do comment if you have any doubts or suggestions on this JS replace topic.

Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.

OS: Windows 10

Code: HTML 5 Version

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