Check if object is a jQuery object

Question

Is there a fast way of checking if an object is a jQuery object or a native JavaScript object?

example:

var o = {}; var e = $('#element');  function doStuff(o) {     if (o.selector) {         console.log('object is jQuery');     } }  doStuff(o); doStuff(e); 

obviously, the code above works but it's not safe. You could potentially add a selector key to the o object and get the same result. Is there a better way of making sure that the object actually is a jQuery object?

Something in line with (typeof obj == 'jquery')

Answer 1

You can use the instanceof operator:

if (obj instanceof jQuery){     console.log('object is jQuery'); } 

Explanation: the jQuery function (aka $) is implemented as a constructor function. Constructor functions are to be called with the new prefix.

When you call $(foo), internally jQuery translates this to new jQuery(foo)¹. JavaScript proceeds to initialize this inside the constructor function to point to a new instance of jQuery, setting it's properties to those found on jQuery.prototype (aka jQuery.fn). Thus, you get a new object where instanceof jQuery is true.

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¹_{It's actually new jQuery.prototype.init(foo): the constructor logic has been offloaded to another constructor function called init, but the concept is the same.}

Answer 2

You may also use the .jquery property as described here: http://api.jquery.com/jquery-2/

var a = { what: "A regular JS object" }, b = $('body');  if ( a.jquery ) { // falsy, since it's undefined     alert(' a is a jQuery object! ');     }  if ( b.jquery ) { // truthy, since it's a string     alert(' b is a jQuery object! '); }