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copied!<p>As far as I could tell it wasn't possible to get the offset of a sub-match automatically, you have to do the calculation yourself using either <code>lastIndex</code> of the RegExp, or the <code>index</code> property of the match object returned by <code>exec()</code>. Depending on which you use you'll either have to add or subtract the length of groups leading up to your sub-match. However, this does mean you have to group the first or last part of the Regular Expression, up to the pattern you wish to locate.</p> <p><code>lastIndex</code> only seems to come into play when using the <code>/g/</code> global flag, and it will record the index after the entire match. So if you wish to use <code>lastIndex</code> you'll need to work backwards from the end of your pattern.</p> <p>For more information on the <code>exec()</code> method, see here:</p> <p><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/exec" rel="nofollow">https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/exec</a></p> <p>The following succinctly shows the solution in operation:</p> <pre><code>var str = '---hello123'; var r = /([a-z]+)([0-9]+)/; var m = r.exec( str ); alert( m.index + m[1].length ); // will give the position of 123 </code></pre> <h3>update</h3> <p>This would apply to your issue using the following:</p> <pre><code>var input = '1234 url( test ) 5678'; var searchedUrl = 'test'; var regexpStr = "(url\\(\\s*)("+searchedUrl+")\\s*\\)"; var regex = new RegExp(regexpStr , 'i'); var match = regex.exec(input); </code></pre> <p>Then to get the submatch offset you can use:</p> <pre><code>match.index + match[1].length </code></pre> <p><code>match[1]</code> now contains <code>url(</code> (plus two spaces) due to the bracket grouping which allows us to tell the internal offset.</p> <h3>update 2</h3> <p>Obviously things are a little more complicated if you have patterns in the RegExp, that you wish to group, before the actual pattern you want to locate. This is just a simple act of adding together each group length.</p> <pre><code>var s = '~- [This may or may not be random|it depends on your perspective] -~'; var r = /(\[)([a-z ]+)(\|)([a-z ]+)(\])/i; var m = r.exec( s ); </code></pre> <p>To get the offset position of <code>it depends on your perspective</code> you would use:</p> <pre><code>m.index + m[1].length + m[2].length + m[3].length; </code></pre> <p>Obviously if you know the RegExp has portions that never change length, you can replace those with hard coded numeric values. However, it's probably best to keep the above <code>.length</code> checks, just in case you — or someone else — ever changes what your expression matches.</p>

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