JavaScript \xdd Metacharacter | Find Character using HexaDecimal Number

The JavaScript \xdd metacharacter is used when we need to match a character using its hexadecimal number (in the form xdd), while working with JavaScript regular expressions. For example:

HTML with JavaScript Code
<!DOCTYPE html>
<html>
<body>

   <p id="xyz"></p>

   <script>
      let myString = "JavaScript is Fun.";
      let pattern = /\x75/;
      document.getElementById("xyz").innerHTML = myString.search(pattern);
   </script>
   
</body>
</html>
Output

The code begins by declaring an empty HTML paragraph element with the ID "xyz".

A string variable "myString" is declared and assigned the value "JavaScript is Fun." in the script section.

The following line declares a regular expression variable "pattern" with the pattern /\x75/. The pattern \x75 corresponds to the Unicode character at position 0x75 (in hexadecimal), which is equivalent to the letter "u".

The string "myString" is then searched using the search() method for the first occurrence of the pattern specified in the "pattern" variable. The position of the first match is returned by the search() method, or -1 if no match is found.

Finally, the position of the first match is set as the content of the HTML paragraph element with the ID "xyz" using the document object's innerHTML property. Because the pattern matches the character "u" in the string "JavaScript is Fun.", the output is the position of the first occurrence of "u," which is 4.

Since the hexadecimal value 75 refers to u. And the index of u in the string is 15. Therefore, the program has produced 15 as output.

Note: The search() function is used to search a substring (value) in a string using a regular expression.

Now, before closing the discussion on the "\xdd" metacharacter while working with the JavaScript RegEx, I'm willing to include one more example that might help you better understand the topic. So here is an example:

HTML with JavaScript Code
<!DOCTYPE html>
<html>
<body>
   <p id="output"></p>

   <script>
      // Declare a string variable containing a hexadecimal escape sequence
      let myString = "\x41\x42\x43";

      // Set the content of the HTML paragraph element with ID "output" to the value of myString
      document.getElementById("output").innerHTML = myString;
   </script>
</body>
</html>
Output
ABC

The "\xdd" metacharacter is used in this example to represent a hexadecimal escape sequence in a string. The escape sequence "\x41\x42\x43" in the string "myString" represents the ASCII characters "A", "B", and "C" in hexadecimal notation.

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