"with" keyword in javascript

Answer 1

just dont use it : http://yuiblog.com/blog/2006/04/11/with-statement-considered-harmful/

Answer 2

I would avoid using it in production code because it's ambiguous but there is an alternative solution to the for-loop-closure solution by using with to mimic the let binding, here's a copy of my previous answer:

An alternative to the standard closure solution using functions inside of a for loop:

<a  href="#">blah</a><br>
<a  href="#">blah</a><br>
<a  href="#">foo</a><br>
<script>
    (function() {
    var anchors = document.getElementsByTagName('a');
        for ( var i = anchors.length; i--; ) {
            var link = anchors[i];
            with ({ number: i }) {
             link.onclick = function() {
                    alert(number);
             };
            }
        }
    })();
</script>

Credit to nlogax for providing a solution which I pretty much ripped off: http://stackoverflow.com/questions/1451009/javascript-infamous-loop-problem

Here's the standard solution:

<script>
    (function() {
    var anchors = document.getElementsByTagName('a');
    for ( var i = anchors.length; i--; ) {
        var link = anchors[i];
        (function(i) {
         link.onclick = function() {
             alert(i)
         }
        })(i);
    }
    })();
</script>

Answer 3

Here are some blog posts in support of the with keyword. But please read the YUI blog entry that azazul posted as well!

http://webreflection.blogspot.com/2009/12/with-worlds-most-misunderstood.html http://webreflection.blogspot.com/2009/12/with-some-good-example.html

Answer 4

Despite advice to the contrary almost everywhere, I think that there are uses for "with". For example, I'm working on a domain model framework for Javascript, which uses the underscore character in much the same way that jQuery uses "$". This means that without "with", I have lots of underscores scattered through my code in ways that make it less readable. Here's a random line from an application using the framework:

_.People().sort(_.score(_.isa(_.Parent)),'Surname','Forename');

whereas with "with" it would look like

with (_) {
    ...

    People().sort(score(isa(Parent)),'Surname','Forename');

    ...
}

What would be really useful is a read-only version of "with".