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Tree shaking
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<h2 id="history">History</h2> <p>Dead code elimination in <a href="/facts/Dynamic_programming_language/j8cQm8RF">dynamic languages</a> is a much harder problem than in static languages. The idea of a "treeshaker" originated in <a href="/facts/LISP/xJHA3CrX">LISP</a><a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> in the 1990s. The idea is that all possible execution flows of a program can be represented as a tree of function calls, so that functions that are never called can be eliminated. </p><p>The algorithm was applied to <a href="/facts/JavaScript/XhhIIEsl">JavaScript</a> in <a href="/facts/Google_Closure_Tools/qs8FBWkj">Google Closure Tools</a> and then to <a href="/facts/Dart_(programming_language)/xJ8tE6Tl">Dart</a> in the dart2js compiler also written by <a href="/facts/Google/GT9Sugza">Google</a>, presented by Bob Nystrom in 2012<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a><a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> and described by the book <i>Dart in Action</i> by author Chris Buckett in 2013: </p> <blockquote><p>When code is converted from Dart to JavaScript the compiler does 'tree shaking'. In JavaScript you have to add an entire library even if you only need it for one function, but thanks to tree shaking the Dart-derived JavaScript only includes the individual functions that you need from a library</p>— Chris Buckett</blockquote> <p>The next wave of popularity of the term is attributed to Rich Harris's Rollup project<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> developed in 2015. </p> <h2 id="relation-to-ecmascript-6-modules">Relation to ECMAScript 6 modules</h2> <p>The popularity of tree shaking in JavaScript is based on the fact that in contrast to CommonJS modules, ECMAScript 6 module loading is static and thus the whole dependency tree can be deduced by statically parsing the syntax tree. Thus tree shaking becomes an easy problem. However, tree shaking does not only apply at the import/export level: it can also work at the statement level, depending on the implementation. </p> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"Reduce JavaScript Payloads with Tree Shaking". <a href="https://developers.google.com/web/fundamentals/performance/optimizing-javascript/tree-shaking#what_is_tree_shakingv" target="_blank">https://developers.google.com/web/fundamentals/performance/optimizing-javascript/tree-shaking#what_is_tree_shakingv</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Harris, Rich (15 January 2019). "Tree-shaking versus dead code elimination". Retrieved 16 September 2020. <a href="https://medium.com/@Rich_Harris/tree-shaking-versus-dead-code-elimination-d3765df85c80" target="_blank">https://medium.com/@Rich_Harris/tree-shaking-versus-dead-code-elimination-d3765df85c80</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Ladd, Seth (29 January 2013). "Minification is not enough, you need tree shaking". Seth Ladd's Blog. <a href="http://blog.sethladd.com/2013/01/minification-is-not-enough-you-need.html" target="_blank">http://blog.sethladd.com/2013/01/minification-is-not-enough-you-need.html</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>comp.lang.lisp What's a treeshaker? <a href="https://groups.google.com/forum/#!topic/comp.lang.lisp/pspFr1XByZk" target="_blank">https://groups.google.com/forum/#!topic/comp.lang.lisp/pspFr1XByZk</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Can Google Dart Solve JavaScript's Speed and Scale Problems? <a href="http://www.cio.com/article/2382855/developer/can-google-dart-solve-javascript-s-speed-and-scale-problems-.html" target="_blank">http://www.cio.com/article/2382855/developer/can-google-dart-solve-javascript-s-speed-and-scale-problems-.html</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Ladd, Seth (29 January 2013). "Minification is not enough, you need tree shaking". Seth Ladd's Blog. <a href="http://blog.sethladd.com/2013/01/minification-is-not-enough-you-need.html" target="_blank">http://blog.sethladd.com/2013/01/minification-is-not-enough-you-need.html</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>How To Clean Up Your JavaScript Build With Tree Shaking <a href="https://web.archive.org/web/20190731133056/https://www.engineyard.com/blog/tree-shaking" target="_blank">https://web.archive.org/web/20190731133056/https://www.engineyard.com/blog/tree-shaking</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> </ol>