How to Check if jQuery Is Loaded on a Page Using JavaScript
Does the current website have jQuery loaded, and if so —which version is loaded? Here’s how to find out if the popular JavaScript library is available on a webpage or in the browser console.
Checking if jQuery Is Loaded With JavaScript
Modern browser consoles have a built-in dollar sign operator ($()) that is an alias for the commonly-used function document.getElementByID(), which selects an HTML element on the page using its ID attribute.
“The dollar sign is commonly used as a shortcut to the function document.getElementById().” — Stephen Chapman at ThoughtCo
Of course, most JavaScript programmers are familiar with the $() function from jQuery, not as an alias of document.getElementByID().
Since any browser console is going to have a $() function, how can you tell if that function is the built-in version or the jQuery version?
The $() function in jQuery is also an alias — this time, for the function jQuery(), which is a selector function more similar to document.getElementsByTagName() than document.getElementByID().
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