decodeURI

decodeURI is a built-in JavaScript function used to decode a Uniform Resource Identifier (URI) that has been previously encoded using encodeURI. The purpose of URI encoding is to represent characters that have special meaning in URIs, or characters that are not allowed in URIs, using a percent-sign escape sequence. decodeURI reverses this process, converting these escape sequences back into their original characters.

For example, if a URI contains a space character, encodeURI would represent it as "%20". Calling decodeURI on a string containing "%20" would return the string with the space character restored. It's important to note that decodeURI only decodes characters that were encoded by encodeURI. It does not decode characters that were encoded by encodeURIComponent, which encodes a broader set of characters, including those that have special meaning in URIs like "/", "?", "&", and "=".

The syntax for decodeURI is simply decodeURI(encodedURIString). The function takes one argument, which is the URI string to be decoded. It returns the decoded URI string. If the input string is not a valid URI, decodeURI might throw a URIError or return the original string depending on the specific invalidity. Generally, decodeURI is used to process user-supplied input or data retrieved from external sources that might contain URI-encoded characters, ensuring that these characters are correctly interpreted within a web context.