Can I use multiple versions of jQuery on the same page?

Recognizing the need

The rationale behind using multiple versions of jQuery is often to ensure that the particular needs of different plugins or scripts are met. As versatile as this may seem, remember to somewhat treat this as a plan B — it should be used when all other options have been exhausted.

Verify before you act

Before you shove another jQuery version onto your page, take a moment to verify if it's already loaded and if so, what the version is:

if (typeof jQuery == 'undefined' || parseFloat(jQuery.fn.jquery) < desiredVersion) {
    // "If not present, load me up, Scotty!"
}
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Doing this can help to maintain a clutter-free page and keep your website running smoothly!

Crafting unique instances

Using $.noConflict(true) allows for multiple independent versions of jQuery:

var v1 = jQuery.noConflict(true);  // A soft spot for legacy parts
var v2 = jQuery.noConflict(true);  // Craving some cutting-edge code
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To segregate your jQuery calls, prefix your scripts with the correct instance variable:

v1('#legacy-widget').oldFunction(); // Relic from the past
v2('#trendy-widget').newFunction(); // New kid on the block
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Managing the Pandora's box

Combining multiple jQuery versions inevitably adds considerable amount of complexity —a good time to weigh the costs vs benefits:

• Functionality vs. maintenance efforts: Is the added functionality worth the additional complexity and the potential headaches?
• Debugging: Keep tabs on the versions in play by dropping the following line of code: console.log($jQ1.fn.jquery);

Wrangling jQuery versions - Best practices

To ensure a well-managed multiple version environment:

1. Devote roles: Let distinct versions handle separate tasks.
2. Specify targets: Use purposeful selectors to avoid overriding.
3. Localize your neighborhood: Engulf your code in Immediately Invoked Function Expressions (IIFE) to prevent global scope pollution.

Exploring other methods

If things get hairy with multiple versions, consider swinging other ways:

• Iframes: Run plugins needing a specific version in separate iframes. Reminder — this may not be the best friend of SEO and usability.
• Webpack: This tool can turn out to be a godsend in managing versioning effectively, given you're in a development environment.