Introduction, comprehensions beyond arrays

Jason Orendorff jason.orendorff at gmail.com
Fri May 10 13:29:20 PDT 2013


To make this a little more concrete, just for fun...

Suppose I make an object representing "all future clicks" and give it a
map() method. This much, of course, is possible already:

    var clicks = {
        map: function (f) {
            document.addEventListener("click", f);
        }
    };

With Mike's proposal, you could write:

    for (let e of clicks) {
        alert(e.clientX + ", " + e.clientY);
    }

This would desugar to:

    clicks.map(e => {
        alert(e.clientX + ", " + e.clientY);
    });

And a listener would be attached to the document. The body of the loop
would run each time the user clicked.

Iterators don't do this.

-j
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