encodeURI()

The encodeURI() function encodes a URI by replacing each instance of certain characters by one, two, three, or four escape sequences representing the UTF-8 encoding of the character (will only be four escape sequences for characters composed of two "surrogate" characters).

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Syntax

encodeURI(URI)

Parameters

URI

A complete URI.

Return value

A new string representing the provided string encoded as a URI.

Description

The encodeURI() function does not encode characters that have special meaning (reserved characters) for a URI. The following example shows all the parts that a URI "scheme" can possibly contain. Note how certain characters are used to signify special meaning:

http://username:password@www.example.com:80/path/to/file.php?foo=316&bar=this+has+spaces#anchor

Hence encodeURI() does not encode characters that are necessary to formulate a complete URI. Also, encodeURI() does not encode a few additional characters, known as "unreserved marks", which do not have a reserved purpose but are allowed in a URI "as is". (See RFC2396)

encodeURI() escapes all characters except:

Not Escaped:

    A-Z a-z 0-9 ; , / ? : @ & = + $ - _ . ! ~ * ' ( ) #

Examples

encodeURI vs encodeURIComponent

encodeURI() differs from encodeURIComponent() as follows:

var set1 = ";,/?:@&=+$#"; // Reserved Characters
var set2 = "-_.!~*'()";   // Unreserved Marks
var set3 = "ABC abc 123"; // Alphanumeric Characters + Space

console.log(encodeURI(set1)); // ;,/?:@&=+$#
console.log(encodeURI(set2)); // -_.!~*'()
console.log(encodeURI(set3)); // ABC%20abc%20123 (the space gets encoded as %20)

console.log(encodeURIComponent(set1)); // %3B%2C%2F%3F%3A%40%26%3D%2B%24%23
console.log(encodeURIComponent(set2)); // -_.!~*'()
console.log(encodeURIComponent(set3)); // ABC%20abc%20123 (the space gets encoded as %20)

Note that encodeURI() by itself cannot form proper HTTP GET and POST requests, such as for XMLHttpRequest, because "&", "+", and "=" are not encoded, which are treated as special characters in GET and POST requests. encodeURIComponent(), however, does encode these characters.

Encoding a lone high surrogate throws

An URIError will be thrown if one attempts to encode a surrogate which is not part of a high-low pair, e.g.,

// high-low pair ok
console.log(encodeURI('\uD800\uDFFF'));

// lone high surrogate throws "URIError: malformed URI sequence"
console.log(encodeURI('\uD800'));

// lone low surrogate throws "URIError: malformed URI sequence"
console.log(encodeURI('\uDFFF'));

Encoding for IPv6

If one wishes to follow the more recent RFC3986 for URLs, which makes square brackets reserved (for IPv6) and thus not encoded when forming something which could be part of a URL (such as a host), the following code snippet may help:

function fixedEncodeURI(str) {
    return encodeURI(str).replace(/%5B/g, '[').replace(/%5D/g, ']');
}

Specifications

Browser compatibility

See also

• decodeURI()
• encodeURIComponent()
• decodeURIComponent()