Question

I was trying to stringify an array-like object that was declared as an array object and found that JSON.stringify wasn’t processing correctly array-like object when it is defined as an array object.

See below for more clarity, –> jsFiddle

var simpleArray = []; //note that it is defined as Array Object 

alert(typeof simpleArray); // returns object -> Array Object

simpleArray ['test1'] = 'test 1';
simpleArray ['test2'] = 'test 2';

alert(JSON.stringify(simpleArray)); //returns [] 

It worked fine and returned me {"test1":"test 1","test2":"test 2"} when I changed

var simpleArray = []; to var simpleArray = {};.

Can someone shed some light or some reference where I can read more?

Edit:

Question: When typeof simpleArray = [] and simpleArray = {} returned object, why JSON.stringify wasn’t able to return {"test1":"test 1","test2":"test 2"} in both cases?

Answer 1

You don’t want an array. When you want an “associative array” in JavaScript, you really want an object, {}.

You can distinguish them with instanceof Array:

[] instanceof Array // true
({}) instanceof Array // false

EDIT: it can process it. It serializes all of the elements of the array. However, to be an element, there must be a numeric key. In this case, there are none.

This is nothing unique to JSON. It’s consistent with toSource and the length property.