JavaScript: detect if argument is array instead of object (Node.JS)

• Array.isArray

native V8 function. It's fast, it's always correct. This is part of ES5.

• arr instanceof Array

Checks whether the object was made with the array constructor.

• _.isArray // underscore method.

A method from underscore. Here is a snippet taken from the their source

var toString = Object.prototype.toString,    nativeIsArray = Array.isArray;_.isArray = nativeIsArray || function(obj) {    return toString.call(obj) === '[object Array]';};

This method takes an object and calls the Object.prototype.toString method on it. This will always return [object Array] for arrays.

In my personal experience I find asking the toString method is the most effective but it's not as short or readable as instanceof Array nor is it as fast as Array.isArray but that's ES5 code and I tend to avoid using it for portability.

I would personally recommend you try using underscore, which is a library with common utility methods in it. It has a lot of useful functions that DRY up your code.

Try this code:

Array.isArray(argument)

How about:

your_object instanceof Array

In V8 in Chrome I get

[] instanceof Array> true({}) instanceof Array> false ({"0":"string","1":"string","length":"2"}) instanceof Array> false