JavaScript - DOM object check array & isArray polyfill

2016-03-22

/posts/2016-03-22-667492/

JavaScript

Table of Contents

# JavaScript - DOM object check array & isArray polyfill

One day my colleague find a question.

ECMA script isArray is not work when object is DOM element

Array.isArray(document.querySelectorAll('div'));
// false

And polyfill for old browser

Object.prototype.toString.call(arg) === '[object Array]';

Still fail

Object.prototype.toString.call(document.getElementsByClassName('product-img'));
// [object HTMLCollection]
Object.prototype.toString.call(document.querySelectorAll('div'));
// [object NodeList]

So i try to make a polyfill

Array.isArray = function(arg) {
    var type = Object.prototype.toString.call(arg);
    if (type === '[object Array]' ||
        type === '[object HTMLCollection]' ||
        type === '[object NodeList]') {
        return true;
    }
    return false;
};