How to know if a URL is decoded/encoded?

Question

I am using Javascript method decodeURIComponent to decode an encoded URL. Now I am having an issue, that sometimes the URL is get encoded twice during redirection between servers, sometimes it is encoded only once.

I want to check that if the URL is still encoded after calling the method decodeURIComponent. How can I do that? Any pointer would be very helpful to me.

Update - 1

If I recursively call a method and check that if the given URL still contains "%", if it contains "%" then decode it and call the method again; and if not return it to the caller, will that work?

Update - 2

For my case I have:

callBackUrl=http%253A%252F%252Fadbc.com%252FPOSM%252Fapp%252Fpages%252Fadf.task-flow%253Fadf.tfDoc%253D%25252FWEB-INF%25252Ftask-flows%25252Fcatalog-edit-task-flow.xml%2526adf.tfId%253Dcatalog%2526_adf.ctrl-state%253Db9akorh22_9%2526articleReference%253D10C00135%2526previousView%253Dcatalog-home%2526fromUCM%253Dtrue%2526articleType%253Dposm%2526developer%253Dcentral

Now I am taking the value of the callBackUrl in my js method, then decoding it and firing window.open() with that decoded URL. the parameters are same and it has:

• adf.tfDoc
• adf.tfId
• articleReference
• previousView
• fromUCM
• articleType
• developer

Parameters into it. So I know there is no query string like value="%..".

Update - 3

I have written the following method:

var decodeURLRecursively = function(url) {
    if(url.indexOf('%') != -1) {
        return decodeURLRecursively(decodeURIComponent(url));
    }

    return url;
}

Answer 1

There is a simple way to konw if a URL string is encoded.

Take the initial string and compare it with the result of decoding it. If the result is the same, the string is not encoded; if the result is different then it is encoded.

I had this issue with my urls and I used this functions:

function isEncoded(uri) {
  uri = uri || '';

  return uri !== decodeURIComponent(uri);
}

So now I can use isEncoded as the discriminant in a while loop (or with recursion) to know if I need to keep calling decodeURIComponent on the string:

function fullyDecodeURI(uri){

  while (isEncoded(uri)){
    uri = decodeURIComponent(uri);
  }

  return uri;
}

This solved the problem for me of decoding urls encoded multiple times. Hope this helps.