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Manual.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="generator" content="Asciidoctor 1.5.4">
<meta name="author" content="Hongbo Zhang">
<title>BuckleScript User Manual</title>
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<body class="article toc2 toc-left">
<div id="header">
<h1><a href="https://github.com/bucklescript/bucklescript">BuckleScript</a> User Manual</h1>
<div class="details">
<span id="author" class="author">Hongbo Zhang</span><br>
<span id="revnumber">version 1.9.0</span>
</div>
<div id="toc" class="toc2">
<div id="toctitle">Table of Contents</div>
<ul class="sectlevel1">
<li><a href="#_why_bucklescript">Why BuckleScript</a>
<ul class="sectlevel2">
<li><a href="#_benefits_of_javascript_platform">Benefits of JavaScript platform</a></li>
<li><a href="#_problems_of_javascript_how_bucklescript_solves_them">Problems of JavaScript && how BuckleScript solves them</a></li>
</ul>
</li>
<li><a href="#_installation">Installation</a>
<ul class="sectlevel2">
<li><a href="#_windows_installation">Windows Installation</a></li>
<li><a href="#__nix_installation">*nix installation</a></li>
<li><a href="#__strong_recommended_strong_installation_with_opam"><strong>Recommended</strong> installation with OPAM</a></li>
<li><a href="#_install_from_source">Install from source</a>
<ul class="sectlevel3">
<li><a href="#_using_npm">using NPM</a></li>
<li><a href="#_minimal_dependencies">Minimal dependencies</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="#_get_started">Get Started</a>
<ul class="sectlevel2">
<li><a href="#_using_existing_templates_since_1_7_4">Using existing templates (@since 1.7.4 )</a></li>
<li><a href="#_first_example_by_hand_without_samples">First example by hand without samples</a></li>
<li><a href="#_an_example_with_multiple_modules">An example with multiple modules</a></li>
</ul>
</li>
<li><a href="#_built_in_npm_support">Built in NPM support</a>
<ul class="sectlevel2">
<li><a href="#_build_an_ocaml_library_as_a_npm_package">Build an OCaml library as a npm package</a></li>
<li><a href="#_to_use_ocaml_library_as_a_npm_package">To use OCaml library as a npm package</a></li>
<li><a href="#_together">Together</a></li>
<li><a href="#_examples">Examples</a></li>
</ul>
</li>
<li><a href="#_js_calling_ocaml">JS Calling OCaml</a></li>
<li><a href="#_bucklescript_annotations_for_unicode_and_js_ffi_support">BuckleScript annotations for Unicode and JS FFI support</a>
<ul class="sectlevel2">
<li><a href="#_unicode_support_since_1_5_1">Unicode support (@since 1.5.1)</a>
<ul class="sectlevel3">
<li><a href="#_unicode_support_with_string_interpolation_since_1_7_0">Unicode support with string interpolation (@since 1.7.0)</a></li>
</ul>
</li>
<li><a href="#_ffi">FFI</a></li>
<li><a href="#_binding_to_simple_js_functions_values">Binding to simple JS functions values</a>
<ul class="sectlevel3">
<li><a href="#_binding_to_global_value_code_bs_val_code">Binding to global value: <code>bs.val</code></a></li>
<li><a href="#_scoped_values_code_bs_scope_code_since_1_7_2">Scoped values: <code>bs.scope</code> (@since 1.7.2)</a></li>
<li><a href="#_binding_to_javascript_constructor_code_bs_new_code">Binding to JavaScript constructor: <code>bs.new</code></a></li>
<li><a href="#_binding_to_a_value_from_a_module_code_bs_module_code">Binding to a value from a module: <code>bs.module</code></a></li>
<li><a href="#_binding_the_whole_module_as_a_value_or_function">Binding the whole module as a value or function</a></li>
<li><a href="#_binding_to_method_code_bs_send_code_code_bs_send_pipe_code">Binding to method: <code>bs.send</code>, <code>bs.send.pipe</code></a></li>
<li><a href="#_binding_to_dynamic_key_access_set_code_bs_set_index_code_code_bs_get_index_code">Binding to dynamic key access/set: <code>bs.set_index</code>, <code>bs.get_index</code></a></li>
<li><a href="#_binding_to_getter_setter_code_bs_get_code_code_bs_set_code">Binding to Getter/Setter: <code>bs.get</code>, <code>bs.set</code></a></li>
</ul>
</li>
<li><a href="#_splice_calling_convention_code_bs_splice_code">Splice calling convention: <code>bs.splice</code></a></li>
<li><a href="#_special_types_on_external_declarations_code_bs_string_code_code_bs_int_code_code_bs_ignore_code_code_bs_as_code_code_bs_unwrap_code">Special types on external declarations: <code>bs.string</code>, <code>bs.int</code>, <code>bs.ignore</code>, <code>bs.as</code>, <code>bs.unwrap</code></a>
<ul class="sectlevel3">
<li><a href="#_using_polymorphic_variant_to_model_enums_and_string_types">Using polymorphic variant to model enums and string types</a></li>
<li><a href="#_using_polymorphic_variant_to_model_event_listener">Using polymorphic variant to model event listener</a></li>
<li><a href="#_using_polymorphic_variant_to_model_arguments_of_multiple_possible_types_since_1_8_3">Using polymorphic variant to model arguments of multiple possible types (@since 1.8.3)</a></li>
<li><a href="#_phantom_arguments_and_ad_hoc_polymorphism">Phantom Arguments and ad-hoc polymorphism</a></li>
<li><a href="#_fixed_arguments">Fixed Arguments</a></li>
<li><a href="#_fixed_arguments_with_arbitrary_json_literal_since_1_7_0">Fixed Arguments with arbitrary JSON literal (@since 1.7.0)</a></li>
</ul>
</li>
<li><a href="#_binding_to_nodejs_special_variables_a_href_api_node_html_bs_node_a">Binding to NodeJS special variables: <a href="../api/Node.html">bs.node</a></a></li>
<li><a href="#_binding_to_callbacks_high_order_function">Binding to callbacks (high-order function)</a>
<ul class="sectlevel3">
<li><a href="#__code_bs_code_for_explicit_uncurried_callback"><code>[@bs]</code> for explicit uncurried callback</a></li>
<li><a href="#__code_bs_uncurry_code_for_implicit_uncurried_callback_since_1_5_0"><code>[@bs.uncurry]</code> for implicit uncurried callback (@since 1.5.0)</a></li>
<li><a href="#_uncurried_calling_convention_as_an_optimization">Uncurried calling convention as an optimization</a>
<ul class="sectlevel4">
<li><a href="#_callback_optimization">Callback optimization</a></li>
</ul>
</li>
<li><a href="#_bindings_to_code_this_code_based_callbacks_code_bs_this_code">Bindings to <code>this</code> based callbacks: <code>bs.this</code></a></li>
</ul>
</li>
<li><a href="#_binding_to_js_objects">Binding to JS objects</a>
<ul class="sectlevel3">
<li><a href="#_simple_object_type">Simple object type</a></li>
<li><a href="#_complex_object_type">Complex object type</a></li>
<li><a href="#_how_to_consume_js_property_and_methods">How to consume JS property and methods</a>
<ul class="sectlevel4">
<li><a href="#_getter_setter_annotation_to_js_properties">getter/setter annotation to JS properties</a></li>
</ul>
</li>
<li><a href="#_create_js_objects_using_bs_obj">Create JS objects using bs.obj</a></li>
<li><a href="#_create_js_objects_using_external">Create JS objects using external</a></li>
<li><a href="#_create_js_objects_with_code_this_code_semantics">Create JS objects with <code>this</code> semantics</a>
<ul class="sectlevel4">
<li><a href="#_method_chaining">Method chaining</a></li>
</ul>
</li>
<li><a href="#_object_label_translation_convention">Object label translation convention</a></li>
</ul>
</li>
<li><a href="#_return_value_checking_since_1_5_1">Return value checking (@since 1.5.1)</a></li>
<li><a href="#_embedding_untyped_javascript_code">Embedding untyped Javascript code</a>
<ul class="sectlevel3">
<li><a href="#_detect_global_variable_existence_code_bs_external_code_since_1_5_1">Detect global variable existence <code>bs.external</code> (@since 1.5.1)</a></li>
<li><a href="#_embedding_arbitrary_js_code_as_an_expression">Embedding arbitrary JS code as an expression</a></li>
<li><a href="#_embedding_raw_js_code_as_statements">Embedding raw JS code as statements</a></li>
</ul>
</li>
<li><a href="#_debugger_support">Debugger support</a></li>
<li><a href="#_regex_support">Regex support</a></li>
<li><a href="#_examples_2">Examples</a>
<ul class="sectlevel3">
<li><a href="#_a_simple_example_binding_to_mocha_unit_test_library">A simple example: binding to mocha unit test library</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="#_exception_handling_between_ocaml_and_js_since_1_7_0">Exception handling between OCaml and JS (@since 1.7.0)</a></li>
<li><a href="#__code_bs_open_code_type_safe_external_data_source_handling_since_1_7_0"><code>bs.open</code>: Type safe external data-source handling (@@since 1.7.0)</a>
<ul class="sectlevel2">
<li><a href="#_use_cases">Use cases</a></li>
</ul>
</li>
<li><a href="#_js_module">Js module</a>
<ul class="sectlevel2">
<li><a href="#_null_and_undefined">Null and Undefined</a></li>
<li><a href="#_boolean">Boolean</a></li>
<li><a href="#_stable_ish_submodules">Stable-ish submodules</a></li>
<li><a href="#_experimental_incomplete_submodules">Experimental/incomplete submodules</a></li>
<li><a href="#_very_experimental_internal_submodules">Very experimental/internal submodules</a></li>
</ul>
</li>
<li><a href="#_node_module">Node module</a>
<ul class="sectlevel2">
<li><a href="#_submodules">Submodules</a></li>
</ul>
</li>
<li><a href="#_extended_compiler_options">Extended compiler options</a>
<ul class="sectlevel2">
<li><a href="#__bs_main_single_directory_build">-bs-main (single directory build)</a></li>
<li><a href="#__bs_files">-bs-files</a></li>
<li><a href="#__bs_package_name">-bs-package-name</a></li>
<li><a href="#__bs_packge_output">-bs-packge-output</a></li>
<li><a href="#__bs_gen_tds">-bs-gen-tds</a></li>
<li><a href="#__bs_no_warn_ffi_type">-bs-no-warn-ffi-type</a></li>
<li><a href="#__bs_eval">-bs-eval</a></li>
<li><a href="#__bs_no_builtin_ppx_ml_bs_no_builtin_ppx_mli">-bs-no-builtin-ppx-ml, -bs-no-builtin-ppx-mli</a></li>
<li><a href="#__bs_no_version_header">-bs-no-version-header</a></li>
</ul>
</li>
<li><a href="#_semantic_differences_from_other_backends">Semantic differences from other backends</a>
<ul class="sectlevel2">
<li><a href="#_custom_data_type">Custom data type</a></li>
<li><a href="#_physical_in_equality">Physical (in)equality</a></li>
<li><a href="#_string_char_range">String char range</a></li>
<li><a href="#_weak_map">Weak map</a></li>
<li><a href="#_integers">Integers</a></li>
<li><a href="#_printf_printf">Printf.printf</a></li>
<li><a href="#_obj_module">Obj module</a></li>
<li><a href="#_hashtbl_hash_algorithm">Hashtbl hash algorithm</a></li>
<li><a href="#_marshall">Marshall</a></li>
<li><a href="#_sys_argv_sys_max_array_length_sys_max_string_length">Sys.argv, Sys.max_array_length, Sys.max_string_length</a></li>
<li><a href="#_unsupported_io_primitives">Unsupported IO primitives</a></li>
</ul>
</li>
<li><a href="#_conditional_compilation_support_static_if">Conditional compilation support - static if</a>
<ul class="sectlevel2">
<li><a href="#_concrete_syntax">Concrete syntax</a></li>
<li><a href="#_typing_rules">Typing rules</a></li>
<li><a href="#_examples_3">Examples</a></li>
<li><a href="#_built_in_variables_and_custom_variables">Built in variables and custom variables</a></li>
<li><a href="#_changes_to_command_line_options">Changes to command line options</a></li>
</ul>
</li>
<li><a href="#_build_system_support">Build system support</a>
<ul class="sectlevel2">
<li><a href="#_bucklescript_build_system_code_bsb_code">BuckleScript build system: <code>bsb</code></a>
<ul class="sectlevel3">
<li><a href="#_build_with_other_bucklescript_dependencies">Build with other BuckleScript dependencies</a></li>
<li><a href="#_mark_your_directory_as_dev_only">Mark your directory as dev only</a></li>
</ul>
</li>
<li><a href="#_a_real_world_example_of_using_code_bsb_code">A real world example of using <code>bsb</code></a></li>
<li><a href="#_namespace_support_since_1_9_0">namespace support (@since 1.9.0)</a></li>
<li><a href="#_in_source_build_support_since_1_9_0">In source build support (@since 1.9.0)</a></li>
<li><a href="#_build_using_make">Build using Make</a></li>
<li><a href="#_customize_rules_generators_support_since_1_7_4">Customize rules (generators support, @since 1.7.4)</a></li>
</ul>
</li>
<li><a href="#_faq">FAQ</a></li>
<li><a href="#_high_level_compiler_workflow">High Level compiler workflow</a>
<ul class="sectlevel2">
<li><a href="#_design_principles">Design Principles</a></li>
<li><a href="#_soundness">Soundness</a></li>
<li><a href="#_minimal_new_symbol_creation">Minimal new symbol creation</a></li>
</ul>
</li>
<li><a href="#_runtime_representation">Runtime representation</a>
<ul class="sectlevel2">
<li><a href="#_simple_ocaml_type">Simple OCaml type</a></li>
</ul>
</li>
<li><a href="#_integration_with_reason">Integration with Reason</a></li>
<li><a href="#_contributions">Contributions</a>
<ul class="sectlevel2">
<li><a href="#_development_set_up">Development set-up</a></li>
<li><a href="#_contributing_to_code_bsb_exe_code">Contributing to <code>bsb.exe</code></a></li>
<li><a href="#_contributing_to_code_bsc_exe_code">Contributing to <code>bsc.exe</code></a></li>
<li><a href="#_contributing_to_the_runtime">Contributing to the runtime</a></li>
<li><a href="#_contributing_to_the_documentation">Contributing to the documentation</a></li>
<li><a href="#_contributing_to_the_api_reference">Contributing to the API reference</a></li>
</ul>
</li>
<li><a href="#_comparisons">Comparisons</a>
<ul class="sectlevel2">
<li><a href="#_difference_from_a_href_https_github_com_ocsigen_js_of_ocaml_js_of_ocaml_a">Difference from <a href="https://github.com/ocsigen/js_of_ocaml">js_of_ocaml</a></a></li>
</ul>
</li>
<li><a href="#_library_api_documentation">Appendix A: Library API documentation</a></li>
<li><a href="#_changes">Appendix B: CHANGES</a>
<ul class="sectlevel2">
<li><a href="#_1_3_2">1.3.2</a></li>
<li><a href="#_1_2_1_dev">1.2.1 + dev</a></li>
<li><a href="#_1_1_2">1.1.2</a></li>
<li><a href="#_1_1_1">1.1.1</a></li>
<li><a href="#_1_03">1.03</a></li>
<li><a href="#_1_02">1.02</a></li>
<li><a href="#_1_01">1.01</a></li>
<li><a href="#_1_0">1.0</a></li>
</ul>
</li>
</ul>
</div>
</div>
<div id="content">
<div id="preamble">
<div class="sectionbody">
<input type="search" id="agolia-search" placeholder="Search docs...">
<!-- at the end of the HEAD -->
<link rel="stylesheet"
href="https://cdn.jsdelivr.net/docsearch.js/2/docsearch.min.css" />
<!-- at the end of the BODY -->
<script type="text/javascript"
src="https://cdn.jsdelivr.net/docsearch.js/2/docsearch.min.js"></script>
<script type="text/javascript"> docsearch({
apiKey: '0fd97db83891aa20810559812d9e69ac',
indexName: 'bucklescript',
inputSelector: '#agolia-search',
debug: false // Set debug to true if you want to inspect the dropdown
});
</script>
<div class="paragraph">
<p>BuckleScript is a backend for the <a href="https://ocaml.org/">OCaml</a> compiler which emits
JavaScript. It works with both vanilla OCaml and <a href="https://github.com/facebook/Reason">Reason</a>, the
whole compiler is compiled into JS (and ASM) so that you can play with it
in the <a href="https://bucklescript.github.io/bucklescript-playground/">browser</a>.</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content">
<div class="paragraph">
<p>Documentation under <a href="https://bucklescript.github.io/bucklescript/Manual.html"><em>bucklescript.github.io</em></a> match the <a href="https://github.com/bucklescript/bucklescript">master branch</a>.</p>
</div>
<div class="paragraph">
<p>If you find errors or omissions in this document, please don’t
hesitate to submit an issue, sources are <a href="https://github.com/bucklescript/bucklescript/tree/master/site/docsource">here</a>.</p>
</div>
</td>
</tr>
</table>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_why_bucklescript"><a class="anchor" href="#_why_bucklescript"></a>Why BuckleScript</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_benefits_of_javascript_platform"><a class="anchor" href="#_benefits_of_javascript_platform"></a>Benefits of JavaScript platform</h3>
<div class="paragraph">
<p>JavaScript is not just <em>the</em> browser language, it’s also the <em>only</em>
existing cross platform language. It is truly everywhere: users don’t
need to install binaries or use package managers to access software,
just a link will work.</p>
</div>
<div class="paragraph">
<p>Another important factor is that the JavaScript VM is quite fast and
keeps getting faster. The JavaScript platform is therefore
increasingly capable of supporting large applications.</p>
</div>
</div>
<div class="sect2">
<h3 id="_problems_of_javascript_how_bucklescript_solves_them"><a class="anchor" href="#_problems_of_javascript_how_bucklescript_solves_them"></a>Problems of JavaScript && how BuckleScript solves them</h3>
<div class="paragraph">
<p>BuckleScript is mainly designed to solve the problems of <em>large scale</em> JavaScript programming:</p>
</div>
<div class="dlist">
<dl>
<dt class="hdlist1">Type-safety</dt>
<dd>
<p>OCaml offers an industrial-strength
state-of-the-art type system and provides very strong type inference (i.e. No
verbose type annotation required compared with TypeScript), which proves
<a href="http://programmers.stackexchange.com/questions/215482/what-are-the-safety-benefits-of-a-type-system">invaluable</a>
in managing large projects. OCaml’s type system is not just for tooling,
it is a <em>sound</em> type system which means it is guaranteed that there will
be no runtime type errors after type checking.</p>
</dd>
<dt class="hdlist1">High quality dead code elimination</dt>
<dd>
<p>A large amount of web-development relies on inclusion of
code dependencies by copying or referencing CDNs (the very thing
that makes JavaScript highly accessible), but this also introduces
a lot of <a href="https://en.wikipedia.org/wiki/Dead_code">dead code</a>. This
impacts performance adversely when the JavaScript VM has to
interpret code that will never be invoked. BuckleScript provides
powerful dead-code elimination at all levels:</p>
<div class="ulist">
<ul>
<li>
<p>Function and module level elimination is facilitated by the
sophistication of the type-system of OCaml and <em>purity analysis</em>.</p>
</li>
<li>
<p>At the global level BuckleScript generates code ready for
dead-code elimination done by bundling tools such as the
<a href="https://developers.google.com/closure/compiler/">Google closure-compiler</a>.</p>
</li>
</ul>
</div>
</dd>
<dt class="hdlist1">Offline optimizations</dt>
<dd>
<p>JavaScript is a dynamic language, it
takes a performance-hit for the VM to optimize code at runtime.
While some JS engines circumvent the problem to some extent by
<a href="http://v8project.blogspot.com/2015/07/code-caching.html">caching</a>,
this is not available to all environments, and lack of a strong
type system also limits the level of optimizations possible. Again,
BuckleScript, using features of the OCaml type-system and compiler
implementation is able to provide many optimizations during offline
compilation, allowing the runtime code to be extremely fast.</p>
</dd>
<dt class="hdlist1">JS platform and Native platform</dt>
<dd>
<p>Run your programs on all platforms, but run your system <em>faster</em>
under specific platforms. JavaScript is everywhere but it does not
mean we have to run all apps in JS, under several platforms, for
example, server side or iOS/Android native apps, when programs are
written in OCaml, it can also be compiled to native code for <em>better
and reliable performance</em>.</p>
</dd>
</dl>
</div>
<div class="paragraph">
<p>While a strong type-system helps in countering these problems, at the
same time we hope to avoid some of the problems faced in using other
offline <a href="https://github.com/jashkenas/coffeescript/wiki/list-of-languages-that-compile-to-js">transpilation systems</a>:</p>
</div>
<div class="dlist">
<dl>
<dt class="hdlist1">Slow compilation</dt>
<dd>
<p>OCaml byte-code compilation is known to be fast
(one or two orders of magnitude faster than other similar languages:
<a href="http://www.scala-lang.org/">Scala</a> or
<a href="https://www.haskell.org/">Haskell</a>),
BuckleScript shares the same property and compiles even faster
since it saves the link time. See the speeds at work in the
<a href="https://bucklescript.github.io/bucklescript-playground/">playground</a>, the native backend is one
order faster than the JS backend.</p>
</dd>
<dt class="hdlist1">Un-readable JS Code and hard to integrate with existing JS libraries</dt>
<dd>
<p>When compiling to JavaScript, many systems
generate code, that while syntactically and semantically correct is
not human-readable and very difficult to debug and profile.
Our BuckleScript implementation and the multi-pass compilation strategy of OCaml,
allows us to avoid <a href="https://en.wikipedia.org/wiki/Name_mangling">name-mangling</a>,
and produce JavaScript code that is human-readable and easier to debug and
maintain. More importantly, this makes integration with existing JS
libraries <em>much easier</em>.</p>
</dd>
<dt class="hdlist1">Large JS output even for a simple program</dt>
<dd>
<p>In BuckleScript, a <code>Hello world</code> program generates <em>20 bytes</em> JS code
instead of <em>50K bytes</em>. This is due to BuckleScript having an excellent
integration with JS libs in that unlike most JS compilers,
all BuckleScript’s runtime is written in OCaml itself so that these
runtime libraries are only needed when user actually calls it.</p>
</dd>
<dt class="hdlist1">Loss of code-structure</dt>
<dd>
<p>Many systems generate JavaScript code that is essentially a
<a href="https://en.wikipedia.org/wiki/Big_ball_of_mud">big ball of mud</a>. We try
to keep the original structure of the code by mapping one OCaml module
to one JS module.</p>
</dd>
</dl>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_installation"><a class="anchor" href="#_installation"></a>Installation</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Below is a list of different ways to install BuckleScript:</p>
</div>
<div class="sect2">
<h3 id="_windows_installation"><a class="anchor" href="#_windows_installation"></a>Windows Installation</h3>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="sh">npm install bs-platform</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="__nix_installation"><a class="anchor" href="#__nix_installation"></a>*nix installation</h3>
<div class="ulist">
<div class="title">Prerequisites</div>
<ul>
<li>
<p>Standard C toolchain</p>
</li>
<li>
<p><code>npm</code> (should be installed with Node)</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>The standard <code>npm</code> package management tool can be used to install
BuckleScript. If you don’t already have <code>npm</code> installed, follow the
directions listed
<a href="https://docs.npmjs.com/getting-started/installing-node">here</a>. Once <code>npm</code>
is installed, run the following command:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="sh">npm install --save bs-platform</code></pre>
</div>
</div>
<div class="paragraph">
<p>or install it globally</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="sh">npm install -g bs-platform</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="__strong_recommended_strong_installation_with_opam"><a class="anchor" href="#__strong_recommended_strong_installation_with_opam"></a><strong>Recommended</strong> installation with OPAM</h3>
<div class="paragraph">
<p>When working with OCaml we also recommend using <a href="https://opam.ocaml.org">opam</a>
package manager to install OCaml toolchains, available
<a href="https://opam.ocaml.org/doc/Install.html">here</a>. You will benefit from the
existing OCaml ecosystem.</p>
</div>
<div class="paragraph">
<p>Once you have <code>opam</code> installed, ask <code>opam</code> to switch to using our
version of the compiler:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="sh">opam update
opam switch 4.02.3+buckle-master
<span class="tok-nb">eval</span> <span class="tok-sb">`</span>opam config env<span class="tok-sb">`</span>
npm install bs-platform</code></pre>
</div>
</div>
<div class="paragraph">
<p>Note that using this approach, the user can also install other OCaml tools easily.</p>
</div>
</div>
<div class="sect2">
<h3 id="_install_from_source"><a class="anchor" href="#_install_from_source"></a>Install from source</h3>
<div class="sect3">
<h4 id="_using_npm"><a class="anchor" href="#_using_npm"></a>using NPM</h4>
<div class="olist arabic">
<div class="title">Prerequisites:</div>
<ol class="arabic">
<li>
<p>Standard C toolchain</p>
</li>
<li>
<p><code>npm</code> (should be installed with Node)</p>
</li>
</ol>
</div>
<div class="listingblock">
<div class="title">Instructions:</div>
<div class="content">
<pre class="pygments highlight"><code data-lang="sh">git clone https://github.com/bucklescript/bucklescript
<span class="tok-nb">cd </span>bucklescript
npm install</code></pre>
</div>
</div>
</div>
<div class="sect3">
<h4 id="_minimal_dependencies"><a class="anchor" href="#_minimal_dependencies"></a>Minimal dependencies</h4>
<div class="olist arabic">
<div class="title">Prerequisites:</div>
<ol class="arabic">