How to check if an object is an array?

Question

I\'m trying to write a function that either accepts a list of strings, or a single string. If it\'s a string, then I want to convert it to an array with just the one item so

Answer 1

Imagine you have this array below:

var arr = [1,2,3,4,5];

Javascript (new and older browsers):

function isArray(arr) {
  return arr.constructor.toString().indexOf("Array") > -1;
}

or

function isArray(arr) {
  return arr instanceof Array;
}

or

function isArray(arr) {
  return Object.prototype.toString.call(arr) === '[object Array]';
}

then call it like this:

isArray(arr);

Javascript (IE9+, Ch5+, FF4+, Saf5+, Opera10.5+)

Array.isArray(arr);

jQuery:

$.isArray(arr);

Angular:

angular.isArray(arr);

Underscore and Lodash:

_.isArray(arr);

Answer 2

You could is isArray method but I would prefer to check with

Object.getPrototypeOf(yourvariable) === Array.prototype

Answer 3

You can check the type of your variable whether it is an array with;

var myArray=[];

if(myArray instanceof Array)
{
....
}

Answer 4

A = [1,2,3]
console.log(A.map==[].map)

In search for shortest version here is what I got so far.

Note, there is no perfect function that will always detect all possible combinations. It is better to know all abilities and limitations of your tools than expect a magic tool.

Answer 5

I would first check if your implementation supports isArray:

if (Array.isArray)
    return Array.isArray(v);

You could also try using the instanceof operator

v instanceof Array

Answer 6

I would make a function to test the type of object you are dealing with...

function whatAmI(me){ return Object.prototype.toString.call(me).split(/\W/)[2]; }

// tests
console.log(
  whatAmI(["aiming","@"]),
  whatAmI({living:4,breathing:4}),
  whatAmI(function(ing){ return ing+" to the global window" }),
  whatAmI("going to do with you?")
);

// output: Array Object Function String

then you can write a simple if statement...

if(whatAmI(myVar) === "Array"){
    // do array stuff
} else { // could also check `if(whatAmI(myVar) === "String")` here to be sure
    // do string stuff
}