Javascript arrays and JQuery .param

Question

I've noticed something weird. I've always thought new Array() was the same as {}, however it seems to be different as {} seems to just be an object type whereas new Array() is an Array in the Chrome debugger.

So I've been using $.param(data), where data is the data from a $.ajax() call. I notice that when i have a params1 = new Array() and a params2 = {} inside the data, they come out differently.

params1 becomes

params1[]=1&params1[]=2

and params2 becomes

params2[0]=1&params2[1]=2.

The problem is that I had been using .param(data, false) because I noticed that params1[] was being serialized incorrectly, however .param(data, false) fails for params2 and gives me params2=[object+Object].

I figure I can get around this by just using .param(data) and stripping out "[]" so that regardless of it being initialized using {} or new Array, it'll still work out correctly. But I'd like to know if there's a better solution (short of always using {} vs new Array).

[] is shorthand for creating a new JavaScript array, not {}. As you already saw, {} creates an empty object. — j08691
– j08691, Commented Aug 8, 2012 at 20:03
possible duplicate of Create an empty object in JavaScript with {} or new Object()? — user1233508
– user1233508, Commented Aug 9, 2012 at 19:17

Matt · Accepted Answer · 2012-08-08 20:08:33Z

1

Kyliod,

In javascript {} is shorthand for creating a new Object, and [] is shorthand for a "new Array()."

SO:

var myArray1 = [];
var myArray2 = new Array();
var myObject = {};
myObject.objVariable1 = 'some string or other variable data';
var myObject2 = { obj2Var1 : 'some string', obj2Var2 : 1234, obj2Var3 : true };

// do stuff

var thing1 = myArray1[1]; // get something out of myArray1
var thing2 = myArray2[2]; // get something out of myArray2
var thing3 = myObject.objVariable1; // get something out of myObject
if(myObject2.obj2Var3)
{
  // do other stuff
}

Hopefully this helps you clear up your jQuery / javascript Ajax issues.

answered Aug 8, 2012 at 20:08

Matt

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