Tree Shaking in JavaScript

Agarwal Peeyush
3 min readJul 10, 2023


Photo by Kawin Harasai on Unsplash

Introduction: The size of our application’s bundle must be optimised in current JavaScript programming in order to boost performance and decrease load times. One method that has drawn a lot of interest is “tree shaking.” We will delve into the idea of “tree shaking,” its advantages, and how it can help your JavaScript application run more efficiently in this blog post.

  1. Understanding Tree Shaking: Static code analysis uses the tree shaking approach to remove useless (or dead) code from the packaged output. It makes use of the module system in JavaScript, where imports and exports may be statically analysed, to locate and eliminate superfluous code during the bundling procedure. Because just the necessary code is supplied, the bundle size is reduced.
  2. How Tree Shaking Works: Tree Shaking uses the static nature of JavaScript modules to do a thorough study of the codebase during the build process. Beginning at the entry point, it moves through the dependency tree and identifies unneeded exports and the dependencies on them as “dead code.” These dead code parts are subsequently removed from the finished bundle using the tree shaking tool.
  3. Benefits of Tree Shaking:
    a. Reduced Bundle Size:
    Tree Shaking considerably decreases the size of the packaged JavaScript file by deleting redundant code. As a result, download times are shortened and application performance is enhanced.
    b. Improved Loading Speed: The client’s browser can load smaller bundles more quickly, improving the user experience overall, particularly in low-bandwidth or mobile network settings.
    c. Optimal Resource Utilization: Tree shaking makes sure that the bundle only contains the necessary code, preventing superfluous modules or functions from unnecessarily using up system resources.
  4. Using Tree Shaking:
    a. ES Modules:
    ES modules work well for tree shaking because their static nature enables precise analysis and the elimination of superfluous code. Be sure to use import and export statements to modularize your source.
    b. Bundler Configuration: The majority of well-known bundlers, including Webpack and Rollup, have tree shaking support built in. To allow tree shaking in your build process, activate the required configuration parameters.
    c. Minification: To further reduce the bundle size and speed up loading, combine tree shaking with compression and code minification approaches.
  5. Considerations and Limitations:
    a. Dynamic Imports:
    Since the dependencies are established at runtime when using dynamically imported modules, tree shaking might not perform as well. When looking for the best tree shaking outcomes, make sure the codebase stays away from pointless dynamic imports.
    b. Side Effects: Tools for shaking trees rely on the supposition that code modules are unaffected by external factors. Even if a module’s exports aren’t being utilised, the tool can be hesitant to remove it if it has unintended side effects (such changing the global state or conducting I/O operations).
    c. Third-Party Libraries: Code that is written in a modular and statically analyzable manner performs tree shaking the best. Since some third-party libraries may have complex dependencies or export patterns that make it challenging for the tool to discover useless code, they might not be well suited for tree shaking.

Conclusion: Tree shaking is an effective method for reducing the size of JavaScript applications’ bundles. Tree shaking improves performance and user experience by removing dead code during the bundling process. This decreases the amount of data that must be downloaded and processed by the client’s browser. To use tree shaking effectively, one must properly configure it, take into account its constraints, and make sure the source is modularized with static imports and exports. Developers can produce smaller, more effective bundles and provide users high-performance applications by using tree shaking and other optimisation techniques.

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