84 lines
2.3 KiB
ReStructuredText
84 lines
2.3 KiB
ReStructuredText
***********
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js_of_ocaml
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***********
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js_of_ocaml_ is a compiler from OCaml to JavaScript. The compiler works by
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translating OCaml bytecode to JS files. From here on, we'll abbreviate
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js_of_ocaml to jsoo. The compiler can be installed with opam:
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.. code:: bash
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$ opam install js_of_ocaml-compiler
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Compiling to JS
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===============
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Dune has full support building jsoo libraries and executables transparently.
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There's no need to customize or enable anything to compile ocaml
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libraries/executables to JS.
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To build a JS executable, just define an executable as you would normally.
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Consider this example:
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.. code:: bash
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echo 'print_endline "hello from js"' > foo.ml
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With the following dune file:
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.. code:: scheme
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(executable (name foo))
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And then request the ``.js`` target:
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.. code:: bash
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$ dune build ./foo.bc.js
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$ node _build/default/foo.bc.js
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hello from js
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Similar targets are created for libraries, but we recommend sticking to the
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executable targets.
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.. _dune-jsoo-field:
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``js_of_ocaml`` field
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=====================
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In ``library`` and ``executables`` stanzas, you can specify js_of_ocaml options
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using ``(js_of_ocaml (<js_of_ocaml-options>))``.
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``<js_of_ocaml-options>`` are all optional:
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- ``(flags <flags>)`` to specify flags passed to ``js_of_ocaml``. This field
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supports ``(:include ...)`` forms
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- ``(javascript_files (<files-list>))`` to specify ``js_of_ocaml`` JavaScript
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runtime files.
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``<flags>`` is specified in the :ref:`ordered-set-language`.
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The default value for ``(flags ...)`` depends on the selected build profile. The
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build profile ``dev`` (the default) will enable sourcemap and the pretty
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JavaScript output.
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Separate Compilation
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====================
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Dune supports two modes of compilation
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- Direct compilation of a bytecode program to JavaScript. This mode allows
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js_of_ocaml to perform whole program deadcode elimination and whole program
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inlining.
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- Separate compilation, where compilation units are compiled to JavaScript
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separately and then linked together. This mode is useful during development as
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it builds more quickly.
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The separate compilation mode will be selected when the build profile is
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``dev``, which is the default. There is currently no other way to control this
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behaviour.
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.. _js_of_ocaml: http://ocsigen.org/js_of_ocaml/
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