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This has a nice name – a lazy function definition. A lazy function is one that pretends to work but it doesn't really.

It does some work initially and then caches the result. Then on consecutive calls it only returns the pre-computed result, it doesn’t really do anything.

In order to do so, the function redefines itself with a new implementation, one that simply points to the computed result.

function lazy() {
    var result = 2 + 2;
    lazy = function() {
        return result;
    };
    return lazy();
}

lazy(); // 4
lazy(); // 4

Tags: Functions, lazy definition

This entry was posted on Tuesday, September 15th, 2009 and is filed under Functions. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.