innerHTML的javascript preg_match

Question

I'm trying to get a link from a page between

url: ' and ',

I have tried a few different solutions found via google but the closest I have got is this

function pregmatch() {
    var re = new RegExp("url: '(.*)',", "g"),// the regex
       txt = 'some text'; // the text on page to be replaced by url
    newtxt = txt.replace(txt,re); // replace text with found url
    document.body.innerHTML = document.body.innerHTML.replace(txt,newtxt);
}
pregmatch();

but this simply replaces the some text with the regex /url: '(.*)',/g and not the url which what is needed.

I also tried newtxt = txt.replace(txt,re[0]); but that came back as undefined, I am a JS novice so any help is appreciated

UPDATE:

Ok I think some miss-understand what I'm trying to do so will try again

In the pages source there is a section:

url: 'http://somedomain.com/b3a4f5d2b725a8d',

On the page itself there is some text hello world which is situated perfectly for where I want to add the url on page, so i want to grab the url from the source and replace the hello world with the url.

ie var txt = 'some text' is not the string from where the url is but infact just text on page that will be replaced with the found url.

Answer 1

The syntax is:

string.replace(regex, replacement);

Thus:

txt.replace(re, somereplacement);

But since you want to get a url, you might be better off using .match :

url = txt.match(re)[1];

And your re would be better with:

var re = new RegExp("url: '(.*?)',", "g");

This prevents matching more than necessary.

Answer 2

You are replacing matches of your regex in string txt with your regular expression.

Correct usage is:

var newtxt = txt.replace(re, "something_to_replace_with");

to get all matches:

var matches = txt.match(re);

Answer 3

Without explicitly defining a regex object:

var reg = /url: '(.*?)',/;
var txt = "url: 'some text',";
if (reg.test(txt))
   alert(txt.match(reg)[1]);

Also be aware that

var txt = 'some text';

Will not match a regular expression looking for single quotes, because the single quotes used above are only used to define the variable as a string -- they don't actually exist as matchable text IN the string itself.