Question

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How to detect if a variable is an array

When I need to test if variable is an array (for example input argument in a function that could be object or array) I usually use this piece of code

typeof(myVar) === 'object' && myVar.length !== undefined;

Is this the correct way or is there a more efficient way, considering that even if myVar instanceof Array is faster it should be avoided due to iframe problem?

Answer 1

Array.isArray is now available with ECMAScript 5, so you can use it with a polyfill for older browsers:

if(!Array.isArray) {
  Array.isArray = function (vArg) {
    return Object.prototype.toString.call(vArg) === "[object Array]";
  };
}

Array.isArray(myVar);