Question

Is it possible to use javascript to add target="_blank" to all links that include the following in the URL: profile.php?id=

Answer 1

The following should work:

var aElems = document.links;

for (var i=0,len = aElems.length; i<len; i++){
    if (aElems[i].href.indexOf('profile.php?id=') != -1){
        aElems[i].target = '_blank';
    }
}

JS Fiddle demo.

---

Edited to improve the performance of the above code, removing document.links and replacing it with document.getElementsByTagName('a'):

var aElems = document.getElementsByTagName('a');

for (var i=0,len = aElems.length; i<len; i++){
    if (aElems[i].href.indexOf('profile.php?id=') != -1){
        aElems[i].target = '_blank';
    }
}

JS Fiddle demo.

---

It’s worth noting, though, that using Chris Fulstow‘s querySelectorAll()-enabled $('a[href*="profile.php?id="]') approach is marginally faster (in Chromium 14/Ubuntu 11.04): JS Perf speed-test. Therefore, the following is the fastest (in browsers that support querySelectorAll()):

var aElems = document.querySelectorAll('a[href*="profile.php?id="]');

for (var i=0,len = aElems.length; i<len; i++){
    if (aElems[i].href.indexOf('profile.php?id=') != -1){
        aElems[i].target = '_blank';
    }
}

JS Fiddle demo.

Above assertion ‘fastest’ supported by JS Perf comparison, at least in Chromium 14/Ubuntu 11.04. Bear in mind, of course, that IE < 8, and Firefox 3, aren’t going to play well with this approach.

Of course, the above should be corrected to:

var aElems = document.querySelectorAll('a[href*="profile.php?id="]');

for (var i=0,len = aElems.length; i<len; i++){
    aElems[i].target = '_blank';
}

JS Fiddle demo.

This is because the if condition was already evaluated by querySelectorAll(), which makes the if entirely redundant.

Modified JS Perf comparison: http://jsperf.com/anchor-selector-test/3.