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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Boa (JavaScript engine)</span></span>
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</style><table class="infobox vevent"><tbody><tr><th colspan="2" class="infobox-above summary">Boa</th></tr><tr><td colspan="2" class="infobox-image logo"><span typeof="mw:File"></span></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="Programmer" title="Programmer">Original author(s)</a></th><td class="infobox-data"><a rel="nofollow" class="external text" href="https://jason-williams.co.uk">Jason Williams</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="Programmer" title="Programmer">Developer(s)</a></th><td class="infobox-data">Boa Developers</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Initial release</th><td class="infobox-data">10 June 2019<span style="display:none"> (<span class="bday dtstart published updated">2019-06-10</span>)</span></td></tr><tr style="display: none;"><td colspan="2" class="infobox-full-data"></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="Software_release_life_cycle" title="Software release life cycle">Stable release</a></th><td class="infobox-data"><div style="margin:0px;">v0.20<sup id="cite_ref-latest-release_1-0" class="reference"><a href="#cite_note-latest-release-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> / 5 December 2024<span style="display:none"> (<span class="bday dtstart published updated">2024-12-05</span>)</span>
/ <span style="display:none"> ()</span></div></td></tr><tr style="display:none"><td colspan="2">
</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="Repository_(version_control)" title="Repository (version control)">Repository</a></th><td class="infobox-data"><span class="url"><a rel="nofollow" class="external text" href="https://github.com/boa-dev/boa">github<wbr>.com<wbr>/boa-dev<wbr>/boa</a></span></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Written in</th><td class="infobox-data"><a href="Rust_(programming_language)" title="Rust (programming language)">Rust</a><sup id="cite_ref-boa-about_2-0" class="reference"><a href="#cite_note-boa-about-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="Computing_platform" title="Computing platform">Platform</a></th><td class="infobox-data"><a href="X86-64" title="X86-64">x86-64</a>, <a href="ARM_architecture" class="mw-redirect" title="ARM architecture">32-bit ARM</a>, <a href="AArch64" title="AArch64">AArch64</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="Software_categories#Categorization_approaches" title="Software categories">Type</a></th><td class="infobox-data"><a href="JavaScript_engine" class="mw-redirect" title="JavaScript engine">JavaScript</a> and <a href="WebAssembly" title="WebAssembly">WebAssembly</a> engine</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="Software_license" title="Software license">License</a></th><td class="infobox-data"><a href="MIT_License" title="MIT License">MIT</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Website</th><td class="infobox-data"><span class="url"><a rel="nofollow" class="external text" href="https://boajs.dev">boajs<wbr>.dev</a></span></td></tr></tbody></table>
<p><b>Boa</b> is an <a href="Open-source" class="mw-redirect" title="Open-source">open-source</a> <a href="JavaScript_engine" class="mw-redirect" title="JavaScript engine">JavaScript</a> engine written in Rust.<sup id="cite_ref-boa-about_2-1" class="reference"><a href="#cite_note-boa-about-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Boa was introduced at JSConf EU 2019 by Jason Williams.<sup id="cite_ref-boa-talk_3-0" class="reference"><a href="#cite_note-boa-talk-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-jsonconf-eu_4-0" class="reference"><a href="#cite_note-jsonconf-eu-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>
</p><p>Williams created Boa in 2017 after working on <a href="Servo_(software)" title="Servo (software)">Servo</a> and being inspired by the "written from scratch" CSS engine.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-jsonconf-eu_4-1" class="reference"><a href="#cite_note-jsonconf-eu-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> He was eager to work on a JavaScript engine using Rust to learn more about how JavaScript implementations work, since then the project has had over 100 contributors.<sup id="cite_ref-boa-talk_3-1" class="reference"><a href="#cite_note-boa-talk-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> Overtime the engine gained more prominent features such as <a href="Bytecode" title="Bytecode">bytecode</a> compilation,<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> better conformance to the specification and ergonomic API design.<sup id="cite_ref-latest-release_1-1" class="reference"><a href="#cite_note-latest-release-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>
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<div class="mw-heading mw-heading2"><h2 id="Design">Design</h2></div>
<p>Boa is an open-source implementation of a JavaScript execution engine. The project is developed as a Rust library for embedding the JavaScript engine in Rust applications. Additionally, the authors of Boa provide a command-line interface (CLI) for users to interact with Boa as standalone JavaScript interpreter accessible from a command line.<sup id="cite_ref-boaspect_8-0" class="reference"><a href="#cite_note-boaspect-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup>
</p><p>Boa follows the common interpreter design which approximately consists of a <a href="Lexer" class="mw-redirect" title="Lexer">lexer</a>, <a href="Parser" class="mw-redirect" title="Parser">parser</a>, <a href="Compiler" title="Compiler">compiler</a> and <a href="Bytecode_interpreter" class="mw-redirect" title="Bytecode interpreter">bytecode interpreter</a><sup id="cite_ref-boaspect_8-1" class="reference"><a href="#cite_note-boaspect-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup>
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<div class="mw-heading mw-heading2"><h2 id="Standards">Standards</h2></div>
<p>Boa implements the ECMA-262 specification (<a href="ECMAScript" title="ECMAScript">ECMAScript</a>). As of 6 September 2024 Boa has 88% conformance to Test262<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup>
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<div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2></div>
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<ul><li><a href="JerryScript" title="JerryScript">JerryScript</a>, an ultra-lightweight JavaScript engine</li>
<li><a href="SpiderMonkey" title="SpiderMonkey">SpiderMonkey</a>, a JavaScript engine used in Firefox</li>
<li><a href="List_of_ECMAScript_engines" class="mw-redirect" title="List of ECMAScript engines">List Of ECMAScript engines</a></li></ul>
<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>
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