Tuesday, April 24, 2012

Javascript's object and associative array duality. A dynamic method invocation feature hiding in plain sight

The duality of Object and associative array in javascript is a neat functionality you can tap anytime

var something = new Object();

something["FirstName"] = "Michael";
something.LastName = "Buen";

something["MiddleName"] = "Ignite";
something.Age = "Forever";




for(var x in something) alert(x + ": " + something[x]);

With that in mind, dynamic method invocation like this is possible:


var arr = ["alert", "confirm"];

for(i = 0; i < arr.length; ++i) window[arr[i]]("Nice!");

And since the alert function is available on implied this object, alert can be done in these ways:

this.alert("would work");
this["alert"]("This would work too");
alert("works"); // the usual

There's another language which has these sort of duality, C language. Its arrays are pointers can be accessed in almost the same ways. Though some might argue that this duality is confusing for beginners.

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