Check if object is a jQuery object

Comprehensive object checking approaches

Your code should be prepared for all sorts of shenanigans, so let's ensure it can firmly answer: "Are you a jQuery object?"

Using the instanceof operator

The instanceof operator is JavaScript's way of saying, "Excuse me, are you of this type?" If obj is indeed a jQuery object, it will politely reply with a true.

// "Are you a jQuery object? Blink twice for yes."
const isJQuery = obj instanceof jQuery;
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Peeking at the .jquery property

The .jquery property is a version string that all jQuery objects carry around like an ID.

// "Ah, you have a .jquery property! Might I see some identification, please?"
const isJQuery = obj && obj.jquery ? true : false;
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This property is great for ID checks, just like a bouncer at a club, except it never has a bad day.

Understanding how $(foo) becomes new jQuery(foo)

It's essential to understand how JavaScript translates $(foo) into new jQuery(foo). This translation process involves an init constructor function that sets up a jQuery object's properties correctly.

Fuss-free check with a utility function

For repeated jQuery object checks, use a utility function. It's like your personal JavaScript butler, always ready to confirm if obj is a jQuery object or not.

function isjQueryObject(obj) {
  // "Dear Butler, is it a jQuery object, or am I seeing things again?"
  return obj instanceof jQuery || (obj && obj.jquery);
}
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More ways to affirm a jQuery object

There are more ways to skin a cat, or in this case, to verify a jQuery object.

The isPrototypeOf() method

If you're into prototype-based checks, the isPrototypeOf() method should be in your toolkit. It's like questioning the DNA of an object.

const isJQuery = jQuery.prototype.isPrototypeOf(obj);
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Short-circuit logic for a speedy verdict

Adding short-circuit logic in your validation keeps the script running smoothly, like a well-oiled machine.

const isJQuery = obj instanceof jQuery || (obj && obj.jquery);
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The first true the statement encounters, it calls it a day.

jQuery version attribute to confirm identity

You can ask an object to show jquery's version attribute, a little like asking, "Do you know the secret handshake?"

const isJQuery = obj && obj.jquery === jQuery.fn.jquery;
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If the versions match, you got your jQuery object.

Checking the constructor property

If you fancy an additional layer of certainty, look at the constructor property.

const isJQuery = obj && obj.constructor && obj.constructor === jQuery;
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It's like meeting someone and subtly asking, "Was your constructor perchance jQuery?"

Mastering the conditionals: JavaScript closures and truthy / falsy values

Alias jQuery within closures

Inside closures or modules, alias jQuery to $. It helps prevent messy naming conflicts and keep a clean scope. Here's how to do it:

(function($) {
  // "$" here strictly stands for jQuery, nothing else.
})(jQuery);
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Understanding truthy and falsy

Knowing how JavaScript treats truthy and falsy values can help you create more robust conditional checks. Is the glass half-empty or half-full? JavaScript can tell you.