Bundle Analysis is a key link in front-end optimization. It can clarify the composition of JavaScript packages, identify redundancy and guide optimization. To quickly view the Bundle composition, you can use Webpack Bundle Analyzer, source-map-explorer, or the corresponding plug-in for the build tool to generate visual charts; prioritize the production environment packaging results during analysis, and save records for easy version comparison. Common problems that cause Bundle bloat include full introduction of third-party libraries, duplicate dependencies, not enabling Tree Shaking, and excessive static resources. Optimization methods include code splitting chunks, configuring Tree Shaking to delete useless code, replacing large-volume libraries with lightweight versions, using automatic plug-ins on demand, and analyzing and eliminating duplicate dependencies. Auxiliary tools such as Source Map Explorer are used for code source analysis, BundlePhobia evaluates dependent volumes, and Lighthouse detects overall loading performance. Combined use of these tools can effectively improve optimization efficiency.

In front-end optimization, Bundle Analysis is a key but often underestimated link. Simply put, it helps you figure out what code your JavaScript package consists of, which part accounts for the majority, whether it is redundant, and whether it is possible to optimize it. If you find that the page loads slowly and the first screen is waiting for a long time, it is likely that the bundle is too large.

The following aspects are the most worthy of attention when doing Bundle Analysis and optimization.

How to quickly view the composition of a Bundle?

The most direct way is to use tools like Webpack Bundle Analyzer . After installation, configure the plug-in and run the packaging command, which will generate a visual treemap diagram that clearly shows the size and dependencies of each module.

In addition to Webpack, Vite, Rollup and other build tools also have similar plug-ins or ecological support. If you are using Create React App, you can directly analyze it through source-map-explorer or webpack-bundle-analyzer plug-in.

A few tips:

• Priority is given to analyzing the packaging results of the production environment. The chunk of the development environment often contains debugging information and is inaccurate.
• Save the analysis results to facilitate comparison of changes between different versions.
• If you use code splitting, remember to analyze the main package and other chunks separately.

What FAQs can cause Bundle to bloat?

After analyzing the bundle, you will find that many "big guys" can actually be optimized. Here are some common questions:

• The third-party library is too large : for example, moment, lodash, chart.js, etc. If only one or two methods are used and fully introduced, it will slow down the loading speed.
• Repeat the same library : For example, multiple dependencies have introduced lodash, but their versions are different, resulting in repeated occurrences during packaging.
• Tree Shaking is not used : Some libraries are not configured correctly, resulting in unused code being packaged.
• Too large static resources such as pictures and fonts : Although these do not belong to JS bundles, their size will also affect the overall loading performance.

The key to solving these problems is: streamlining dependency, introducing on demand, and reasonably splitting .

How to optimize the Bundle volume?

Optimizing a Bundle is not just "delete code", but requires strategic control of the packaged content. Here are some practical practices:

• Use Code Splitting : Split unimportant pages or components into separate chunks and load them on demand.
• Tree Shaking configuration is in place : Make sure your build tools recognize and remove useless code.
• Replace large-volume libraries as lightweight alternatives : for example, replace moment with day.js and replace part of fetch encapsulation with axios.
• Use automatic on-demand import plug-ins : such as babel-plugin-import, which automatically introduces component libraries (such as Ant Design) on-demand.
• Analyze duplicate dependencies : Use depcheck or yarn why to see which dependencies are introduced multiple times, try to unify the version or eliminate unnecessary dependencies.

For example, if you use lodash but only map and filter , you can consider introducing only these two methods:

 import map from 'lodash/map';
import filter from 'lodash/filter';

Or use lodash-es Tree Shaking to automatically optimize.

What tools can assist in analysis and optimization?

In addition to the aforementioned Webpack Bundle Analyzer, there are some other tools that can help you understand your packaging situation more comprehensively:

• Source Map Explorer : Analyze the source of the final code through source map, which is suitable for troubleshooting which part of the code occupies volume.
• BundlePhobia : Enter the npm package name, which will tell you the volume and compressed size of the package, helping you evaluate the impact before introducing new dependencies.
• Lighthouse : Although it is not a tool that specializes in analyzing bundles, its "performance" score can tell you whether the loading speed meets the standard and indirectly reflect whether the bundle is reasonable.

These tools work together to let you understand your front-end resources from multiple perspectives.

Basically that's it. Bundle Analysis seems to be a technical job, but in fact, as long as you master a few key points, you can quickly discover problems and optimize them. Don't underestimate these details, their impact on loading speed and user experience is often greater than you think.

The above is the detailed content of Bundle Analysis for Frontend Optimization. For more information, please follow other related articles on the PHP Chinese website!