I want to decode a string that has been encoded using the java.net.URLEncoder.encode() method.
I tried using the unescape() function in javascript, but a problem occurs for blank spaces because java.net.URLEncoder.encode() converts a blank space
to '+' but unescape() won't convert '+' to a blank space.
Using JavaScript's escape/unescape function is almost always the wrong thing, it is incompatible with URL-encoding or any other standard encoding on the web. Non-ASCII characters are treated unexpectedly as well as spaces, and older browsers don't necessarily have the same behaviour.
As mentioned by roenving, the method you want is decodeURIComponent(). This is a newer addition which you won't find on IE 5.0, so if you need to support that browser (let's hope not, nowadays!) you'd need to implement the function yourself. And for non-ASCII characters that means you need to implement a UTF-8 encoder. Code is available if you need it.
decodeURI[Component] doesn't handle + as space either (at least on FF3, where I tested).
Simple workaround:
alert(decodeURIComponent('http://foo.com/bar+gah.php?r=%22a+b%22&d=o%e2%8c%98o'.replace(/\+/g, '%20')))
Indeed, unescape chokes on this URL: it knows only UTF-16 chars like %u2318 which are not standard (see Percent-encoding).
Try
var decoded = decodeURIComponent(encoded.replace(/\+/g," "));
