Better RegEx to extract GoogleVideo ID from URL

Question

HI!

I use this the following regex with JS to extract this id 6321890784249785097 from that url

http://video.google.com/googleplayer.swf?docId=6321890784249785097

url.replace(/^[^\$]+.(.{19}).*/,"$1");

But I only cut the last 19 chars from the tail. How can I make to more bullet-proof? Maybe with an explanation so that I learn something?

Answer 1

url.replace(/.*docId=(\d{19}).*/i,"$1");

this cuts 19 digits that follow docId=.

Answer 2

video[.]google[.]com/googleplayer[.]swf[?]docId=(\d+)

The ID will be captured in reference #1. If you just want to match 19 digits you can chance it to this:

video[.]google[.]com/googleplayer[.]swf[?]docId=(\d{19})

Answer 3

This should work a bit better:

/^.*docId=(\d+)$/

This matches all characters up to the 'docId=', then gives you all digits after that up to the end of the url.

Answer 4

Here is the function I use in our app to read url parameters. So far it didn't let me down ;)

urlParam:function(name, w){
    w = w || window;
    var rx = new RegExp('[\&|\?]'+name+'=([^\&\#]+)'),
        val = w.location.href.match(rx);
    return !val ? '':val[1];
}

For the explanation of the regexp:

• [\&|\?] take either the start of the query string '?' or the separation between parameters '&'
• 'name' will be the name of the parameter 'docId' in your case
• ([^\&#]+) take any characters that are not & and #.
  The hash key is often used in one page apps.
  And the parenthesis keep the reference of the content.
• val will be an array or null/undefined and val[1] the value you are looking for