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JavaScript - RegExp exec Method

The JavaScript RegExp.exec() method is used to search a string for a specified pattern defined by the regular expression. If the match is found, it returns an array with the matched text, otherwise, it will return null in the result.

In JavaScript, a regular expression (RegExp) is an object that describes a sequence of characters used for defining a search pattern. The best use of regular expressions is for form validation. When users submit data through forms (such as input fields), you can apply regular expressions to ensure that the data meets specific criteria.

Syntax

Following is the syntax of JavaScript RegExp.exec() method −

RegExp.exec(str)

Parameters

This method accepts a parameter named 'str', which is described below −

  • str − The string needs to be searched.

Return value

This method returns an array containing the matched text, If a match is found. Otherwise, it will return a null value.

Examples

If a match is found, this method will return an array that contains the matched text.

Example 1

In the following example, we are using the JavaScript RegExp.exec() method to search a string for a pattern ('to*', 'g') defined by the regular expression within the string "Tutorials point".

<html>
<head>
   <title>JavaScript RegExp.exec() Method</title>
</head>
<body>
   <script>
      const regex = RegExp('to*', 'g');
      const str = "Tutorials point";
      document.write("The string to be searched: ", str);
      document.write("<br>The regex: ", regex);
      let arr = {};
      arr = regex.exec(str);
      document.write("<br>An array with matched text: ", arr);
      document.write("<br>The array length: ", arr.length);
   </script>
</body>
</html>

Output

The above program returns an array with matched text.

The string to be searched: Tutorials point
The regex: /to*/g
An array with matched text: to
The array length: 1

Example 2

If there is no match found, the method will return null.

The following is another example of the JavaScript RegExp.exec() method. We use this method to search a string for a pattern ('/mn\*', 'g') defined by the regular expression within this string "Virat is a damn good batsman".

<html>
<head>
   <title>JavaScript RegExp.exec() Method</title>
</head>
<body>
   <script>
      const regex = RegExp('/mn\*', 'g');
      const str = "Virat is a damn good batsman";
      document.write("The string to be searched: ", str);
      document.write("<br>The regex: ", regex);
      let arr = {};
      arr = regex.exec(str);
      document.write("<br>An array with matched text: ", arr);
      document.write("<br>The array length: ", arr.length);
   </script>
</body>
</html>

Output

After executing the above program, it will return null.

The string to be searched: Virat is a damn good batsman
The regex: /\/mn*/g
An array with matched text: null

Example 3

We can use the result of this method in the conditional statement to check whether a match is found or not.

<html>
<head>
   <title>JavaScript RegExp.exec() Method</title>
</head>
<body>
   <script>
      const regex = RegExp('\llo*', 'g');
      const str = "Hello World";
      document.write("The string to be searched: ", str);
      document.write("<br>The regex: ", regex);
      let result = {};
      result = regex.exec(str);
      
      //using method result in conditional statement....
      if(result != null){
         document.write("<br>The string '" + result[0] + "' found.")
      } else {
         document.write("<br>Not found...");
      }
   </script>
</body>
</html>

Output

Once the above program is executed, it will return a statement based on the condition −

The string to be searched: Hello World
The regex: /llo*/g
The string 'llo' found.
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