Why does this associative array return undefined?

I don't know why this isn't working. I thought I've seen this in use a dozen times but it appears that I looked at it the wrong 开发者_如何转开发way judging from this:

var array = ["dog", "cat"];
console.log(array["dog"]); // undefined, why?

var array = {dog: "dog", cat: "cat"};
console.log(array["dog"]); // defined, why?

What you have is not an associative array, it does not act as such. A JavaScript object acts as such. The object's literals are {}, not [].

Because you haven't set a value for the key "dog".

var array = {"dog":"woof", "cat":"meow"}
console.log(array["dog"]); // returns woof

That's not an associative array. As a matter of fact, associative arrays don't exist in JavaScript. If you want something which behaves similarly, use an object:

var animals = {dog: 123, cat: 456};
console.log(animals["dog"], animals.dog);

You've made an array with two elements:

array[0] = 'dog'
array[1] = 'cat'

This is not an associative array.

its not an associative array, just a regular array.

console.log(array[0]); // will give you dog

if you want associative array behavior create an object like so:

var dictionary = {"dog":"woof", "cat":"meow"};
console.log(dictionary["dog"]);