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decodeURIComponent() function in JavaScript
The decodeURIComponent() function accepts a string value representing an encoded URI (Uniform Resource Identifier), decodes it, and returns the result. It reverses the encoding done by encodeURIComponent().
Syntax
decodeURIComponent(encodedURI)
Parameters
encodedURI: A string representing an encoded URI component that you want to decode.
Return Value
Returns a new string representing the decoded version of the given encoded URI component.
Example
<html>
<head>
<title>JavaScript Example</title>
</head>
<body>
<script type="text/javascript">
var encodedData = encodeURIComponent('http://www.qries.com/?x=?????');
document.write("Encoded Data: " + encodedData);
document.write("<br>");
var decodedData = decodeURIComponent(encodedData);
document.write("Decoded Data: " + decodedData);
</script>
</body>
</html>
Output
Encoded Data: http%3A%2F%2Fwww.qries.com%2F%3Fx%3D%D1%88%D0%B5%D0%BB%D0%BB%D1%8B Decoded Data: http://www.qries.com/?x=?????
Common Use Cases
<html>
<head>
<title>decodeURIComponent Examples</title>
</head>
<body>
<script type="text/javascript">
// Decoding special characters
var encoded1 = "Hello%20World%21";
document.write("Decoded: " + decodeURIComponent(encoded1));
document.write("<br>");
// Decoding email addresses
var encoded2 = "user%40example.com";
document.write("Email: " + decodeURIComponent(encoded2));
document.write("<br>");
// Decoding query parameters
var encoded3 = "name%3DJohn%26age%3D25";
document.write("Query: " + decodeURIComponent(encoded3));
</script>
</body>
</html>
Output
Decoded: Hello World! Email: user@example.com Query: name=John&age=25
Error Handling
If the input contains invalid percent-encoded sequences, decodeURIComponent() throws a URIError:
<html>
<head>
<title>Error Handling Example</title>
</head>
<body>
<script type="text/javascript">
try {
var result = decodeURIComponent("%E0%A4%A"); // Invalid sequence
document.write("Result: " + result);
} catch (error) {
document.write("Error: " + error.name + " - " + error.message);
}
</script>
</body>
</html>
Output
Error: URIError - URI malformed
Conclusion
The decodeURIComponent() function is essential for processing URL-encoded data in web applications. Always use try-catch blocks when decoding untrusted input to handle potential URIError exceptions.
Updated on: 2026-03-15T23:18:59+05:30
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