Array Type

We’ve seen throughout this chapter that arrays are objects with some special behavior. Given an unknown object, it is often useful to be able to determine whether it is an array or not. In ECMAScript 5, you can do this with the Array.isArray() function:

Array.isArray([])     // => true
Array.isArray({})     // => false

We can write an isArray() function that works in any version of JavaScript like this:

var isArray = Array.isArray || function(o) {
    var ts = Object.prototype.toString;
    return typeof o === "object" &&
 	   ts.call(o) === "[object Array]";
};