Use Modernizr responsibly: Strategies to Improve Website Performance

Modernizr, a JavaScript library that can detect whether the browser supports specific features. However, to avoid slowing down the website, be sure to use it with caution. This article explores how to use Modernizr responsibly, as well as other similar libraries such as jQuery.

Why pay attention to how Modernizr loads?

A key question: Are you willing to wait for seconds to access the web page? If the answer is no, so will your visitors. Long loading times will directly affect the user experience and lead to loss of visitors. Therefore, even if you pursue cool features, you must take into account the performance of the website.

The key is how to load. Many JavaScript files are executed after the page is loaded, and putting them in is meaningless, and will block page rendering. Large scripts are placed in , and visitors must wait for the script to load before they can see the page content.

Modernizr is used to detect modern features such as CSS transitions and transformations. Except for special circumstances, these characteristics are not necessary to display page content. Most of the time, Modernizr can be loaded at the end of instead of .

Optimization is not only for a single resource

If a webpage using Modernizr is loading slowly, simply loading the library responsibly may not be enough to solve the performance problem. A responsible approach means careful consideration every time you include a JavaScript file or other large resources. Optimizing a single resource may not be obvious, but optimizing all resources can significantly improve performance.

Clarify the needs

Be sure to clarify the requirements before using Modernizr. Modernizr offers many tests, but not all tests are useful for your project. Modernizr official website provides custom build tools, you can select only the necessary tests to generate smaller custom versions, thereby reducing download time.

It is recommended to use the full version of Modernizr during the project development stage and regenerate a custom version when it is released. A better approach is to use automation tools such as grunt-modernizr, which scans your CSS and JavaScript files, finds out all the features used, and generates corresponding custom Modernizr builds.

Not all tests are necessary

For example, Modernizr can test whether the browser supports the text-shadow CSS attribute. If not supported, this property will be ignored and will not cause the website to crash. Therefore, unless text-shadow is critical to your website (for example, to improve text readability), the test may not be necessary.

For situations where a fallback scheme is needed, you still need to test it, but not all fallback schemes require Modernizr. Some CSS fallback schemes do not require testing themselves.

html5shiv Used to support HTML5 elements in older versions of Internet Explorer. Modernizr can include it, but you don't need it if you are not compatible with older IE. It is recommended to use html5shiv, but it does not have to be loaded through Modernizr. You can consider loading through conditional annotations or inline scripts.

Some functions can delay loading

Most Modernizr features can be delayed loading to the bottom of the page. This does not prevent users from seeing the page content, but instead displays the basic content first and then loads the enhanced experience.

However, certain features, such as html5shiv, must be placed in to be loaded before rendering HTML5 elements. But you can optimize how it loads through conditional comments or inline scripts to reduce HTTP requests.

Deciding whether to place Modernizr in depends on your page structure and functionality. If the test results do not affect the page layout, you can delay loading.

Efficiency consideration

While putting Modernizr at the bottom of the page can improve loading time, Paul Irish points out that many Modernizr tests (especially CSS tests) can cause reflows, causing the browser to recalculate the style, which may offset the delay Benefits of loading.

It depends on the complexity of your DOM tree. In the case of simpler DOM trees, the test execution is faster. It is recommended to conduct tests to evaluate execution time under different browsers and versions. Custom builds can reduce unnecessary testing and further improve efficiency.

Summary

This article explores how to use Modernizr responsibly and how to choose the right loading location in different situations. No matter which method you choose, unnecessary resource downloads should be minimized to provide users with a good experience, especially when the network connection is slow. This responsible development approach is not only for Modernizr, but also for other libraries such as jQuery. Avoiding downloading of useless data is a principle that every developer should follow.

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