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<ol class="chapter"><li class="affix"><a href="../introduction.html">Introduction</a></li><li class="spacer"></li><li><a href="../examples/index.html"><strong aria-hidden="true">1.</strong> Examples</a></li><li><ol class="section"><li><a href="../examples/hello-world.html"><strong aria-hidden="true">1.1.</strong> Hello, World!</a></li><li><a href="../examples/console-log.html"><strong aria-hidden="true">1.2.</strong> Using console.log</a></li><li><a href="../examples/add.html"><strong aria-hidden="true">1.3.</strong> Small wasm files</a></li><li><a href="../examples/without-a-bundler.html"><strong aria-hidden="true">1.4.</strong> Without a Bundler</a></li><li><a href="../examples/wasm2js.html"><strong aria-hidden="true">1.5.</strong> Converting WebAssembly to JS</a></li><li><a href="../examples/import-js.html"><strong aria-hidden="true">1.6.</strong> Importing functions from JS</a></li><li><a href="../examples/char.html"><strong aria-hidden="true">1.7.</strong> Working with char</a></li><li><a href="../examples/wasm-in-wasm.html"><strong aria-hidden="true">1.8.</strong> js-sys: WebAssembly in WebAssembly</a></li><li><a href="../examples/dom.html"><strong aria-hidden="true">1.9.</strong> web-sys: DOM hello world</a></li><li><a href="../examples/closures.html"><strong aria-hidden="true">1.10.</strong> web-sys: Closures</a></li><li><a href="../examples/performance.html"><strong aria-hidden="true">1.11.</strong> web-sys: performance.now</a></li><li><a href="../examples/fetch.html"><strong aria-hidden="true">1.12.</strong> web-sys: using fetch</a></li><li><a href="../examples/2d-canvas.html"><strong aria-hidden="true">1.13.</strong> web-sys: canvas hello world</a></li><li><a href="../examples/julia.html"><strong aria-hidden="true">1.14.</strong> web-sys: canvas Julia set</a></li><li><a href="../examples/web-audio.html"><strong aria-hidden="true">1.15.</strong> web-sys: WebAudio</a></li><li><a href="../examples/webgl.html"><strong aria-hidden="true">1.16.</strong> web-sys: WebGL</a></li><li><a href="../examples/websockets.html"><strong aria-hidden="true">1.17.</strong> web-sys: WebSockets</a></li><li><a href="../examples/webrtc_datachannel.html"><strong aria-hidden="true">1.18.</strong> web-sys: WebRTC DataChannel</a></li><li><a href="../examples/request-animation-frame.html"><strong aria-hidden="true">1.19.</strong> web-sys: requestAnimationFrame</a></li><li><a href="../examples/paint.html"><strong aria-hidden="true">1.20.</strong> web-sys: A Simple Paint Program</a></li><li><a href="../examples/raytrace.html"><strong aria-hidden="true">1.21.</strong> Parallel Raytracing</a></li><li><a href="../examples/todomvc.html"><strong aria-hidden="true">1.22.</strong> web-sys: A TODO MVC App</a></li></ol></li><li><a href="../reference/index.html"><strong aria-hidden="true">2.</strong> Reference</a></li><li><ol class="section"><li><a href="../reference/deployment.html"><strong aria-hidden="true">2.1.</strong> Deployment</a></li><li><a href="../reference/js-snippets.html"><strong aria-hidden="true">2.2.</strong> JS snippets</a></li><li><a href="../reference/passing-rust-closures-to-js.html"><strong aria-hidden="true">2.3.</strong> Passing Rust Closures to JS</a></li><li><a href="../reference/receiving-js-closures-in-rust.html"><strong aria-hidden="true">2.4.</strong> Receiving JS Closures in Rust</a></li><li><a href="../reference/js-promises-and-rust-futures.html"><strong aria-hidden="true">2.5.</strong> Promises and Futures</a></li><li><a href="../reference/iterating-over-js-values.html"><strong aria-hidden="true">2.6.</strong> Iterating over JS Values</a></li><li><a href="../reference/arbitrary-data-with-serde.html" class="active"><strong aria-hidden="true">2.7.</strong> Arbitrary Data with Serde</a></li><li><a href="../reference/accessing-properties-of-untyped-js-values.html"><strong aria-hidden="true">2.8.</strong> Accessing Properties of Untyped JS Values</a></li><li><a href="../reference/working-with-duck-typed-interfaces.html"><strong aria-hidden="true">2.9.</strong> Working with Duck-Typed Interfaces</a></li><li><a href="../reference/cli.html"><strong aria-hidden="true">2.10.</strong> Command Line Interface</a></li><li><a href="../reference/optimize-size.html"><strong aria-hidden="true">2.11.</strong> Optimizing for Size</a></li><li><a href="../reference/rust-targets.html"><strong aria-hidden="true">2.12.</strong> Supported Rust Targets</a></li><li><a href="../reference/browser-support.html"><strong aria-hidden="true">2.13.</strong> Supported Browsers</a></li><li><a href="../reference/types.html"><strong aria-hidden="true">2.14.</strong> Supported Types</a></li><li><ol class="section"><li><a href="../reference/types/imported-js-types.html"><strong aria-hidden="true">2.14.1.</strong> Imported JavaScript Types</a></li><li><a href="../reference/types/exported-rust-types.html"><strong aria-hidden="true">2.14.2.</strong> Exported Rust Types</a></li><li><a href="../reference/types/jsvalue.html"><strong aria-hidden="true">2.14.3.</strong> JsValue</a></li><li><a href="../reference/types/boxed-jsvalue-slice.html"><strong aria-hidden="true">2.14.4.</strong> Box<[JsValue]></a></li><li><a href="../reference/types/pointers.html"><strong aria-hidden="true">2.14.5.</strong> *const T and *mut T</a></li><li><a href="../reference/types/numbers.html"><strong aria-hidden="true">2.14.6.</strong> Numbers</a></li><li><a href="../reference/types/bool.html"><strong aria-hidden="true">2.14.7.</strong> bool</a></li><li><a href="../reference/types/char.html"><strong aria-hidden="true">2.14.8.</strong> char</a></li><li><a href="../reference/types/str.html"><strong aria-hidden="true">2.14.9.</strong> str</a></li><li><a href="../reference/types/string.html"><strong aria-hidden="true">2.14.10.</strong> String</a></li><li><a href="../reference/types/number-slices.html"><strong aria-hidden="true">2.14.11.</strong> Number Slices</a></li><li><a href="../reference/types/boxed-number-slices.html"><strong aria-hidden="true">2.14.12.</strong> Boxed Number Slices</a></li><li><a href="../reference/types/result.html"><strong aria-hidden="true">2.14.13.</strong> Result<T, JsValue></a></li></ol></li><li><a href="../reference/attributes/index.html"><strong aria-hidden="true">2.15.</strong> #[wasm_bindgen] Attributes</a></li><li><ol class="section"><li><a href="../reference/attributes/on-js-imports/index.html"><strong aria-hidden="true">2.15.1.</strong> On JavaScript Imports</a></li><li><ol class="section"><li><a href="../reference/attributes/on-js-imports/catch.html"><strong aria-hidden="true">2.15.1.1.</strong> catch</a></li><li><a href="../reference/attributes/on-js-imports/constructor.html"><strong aria-hidden="true">2.15.1.2.</strong> constructor</a></li><li><a href="../reference/attributes/on-js-imports/extends.html"><strong aria-hidden="true">2.15.1.3.</strong> extends</a></li><li><a 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class="section"><li><a href="../reference/attributes/on-rust-exports/constructor.html"><strong aria-hidden="true">2.15.2.1.</strong> constructor</a></li><li><a href="../reference/attributes/on-rust-exports/js_name.html"><strong aria-hidden="true">2.15.2.2.</strong> js_name = Blah</a></li><li><a href="../reference/attributes/on-rust-exports/readonly.html"><strong aria-hidden="true">2.15.2.3.</strong> readonly</a></li><li><a href="../reference/attributes/on-rust-exports/skip.html"><strong aria-hidden="true">2.15.2.4.</strong> skip</a></li><li><a href="../reference/attributes/on-rust-exports/start.html"><strong aria-hidden="true">2.15.2.5.</strong> start</a></li><li><a href="../reference/attributes/on-rust-exports/typescript_custom_section.html"><strong aria-hidden="true">2.15.2.6.</strong> typescript_custom_section</a></li><li><a href="../reference/attributes/on-rust-exports/getter-and-setter.html"><strong aria-hidden="true">2.15.2.7.</strong> getter and setter</a></li><li><a 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Translations</a></li><li><a href="../web-sys/inheritance.html"><strong aria-hidden="true">3.5.</strong> Inheritance</a></li><li><a href="../web-sys/unstable-apis.html"><strong aria-hidden="true">3.6.</strong> Unstable APIs</a></li></ol></li><li><a href="../wasm-bindgen-test/index.html"><strong aria-hidden="true">4.</strong> Testing with wasm-bindgen-test</a></li><li><ol class="section"><li><a href="../wasm-bindgen-test/usage.html"><strong aria-hidden="true">4.1.</strong> Usage</a></li><li><a href="../wasm-bindgen-test/asynchronous-tests.html"><strong aria-hidden="true">4.2.</strong> Writing Asynchronous Tests</a></li><li><a href="../wasm-bindgen-test/browsers.html"><strong aria-hidden="true">4.3.</strong> Testing in Headless Browsers</a></li><li><a href="../wasm-bindgen-test/continuous-integration.html"><strong aria-hidden="true">4.4.</strong> Continuous Integration</a></li></ol></li><li><a href="../contributing/index.html"><strong aria-hidden="true">5.</strong> Contributing to wasm-bindgen</a></li><li><ol class="section"><li><a href="../contributing/testing.html"><strong aria-hidden="true">5.1.</strong> Testing</a></li><li><a href="../contributing/design/index.html"><strong aria-hidden="true">5.2.</strong> Internal Design</a></li><li><ol class="section"><li><a href="../contributing/design/js-objects-in-rust.html"><strong aria-hidden="true">5.2.1.</strong> JS Objects in Rust</a></li><li><a href="../contributing/design/exporting-rust.html"><strong aria-hidden="true">5.2.2.</strong> Exporting a function to JS</a></li><li><a href="../contributing/design/exporting-rust-struct.html"><strong aria-hidden="true">5.2.3.</strong> Exporting a struct to JS</a></li><li><a href="../contributing/design/importing-js.html"><strong aria-hidden="true">5.2.4.</strong> Importing a function from JS</a></li><li><a href="../contributing/design/importing-js-struct.html"><strong aria-hidden="true">5.2.5.</strong> Importing a class from JS</a></li><li><a href="../contributing/design/rust-type-conversions.html"><strong aria-hidden="true">5.2.6.</strong> Rust Type conversions</a></li><li><a href="../contributing/design/describe.html"><strong aria-hidden="true">5.2.7.</strong> Types in wasm-bindgen</a></li></ol></li><li><a href="../contributing/js-sys/index.html"><strong aria-hidden="true">5.3.</strong> js-sys</a></li><li><ol class="section"><li><a href="../contributing/js-sys/testing.html"><strong aria-hidden="true">5.3.1.</strong> Testing</a></li><li><a href="../contributing/js-sys/adding-more-apis.html"><strong aria-hidden="true">5.3.2.</strong> Adding More APIs</a></li></ol></li><li><a href="../contributing/web-sys/index.html"><strong aria-hidden="true">5.4.</strong> web-sys</a></li><li><ol class="section"><li><a href="../contributing/web-sys/overview.html"><strong aria-hidden="true">5.4.1.</strong> Overview</a></li><li><a href="../contributing/web-sys/testing.html"><strong aria-hidden="true">5.4.2.</strong> Testing</a></li><li><a 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<main>
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<h1><a class="header" href="#serializing-and-deserializing-arbitrary-data-into-and-from-jsvalue-with-serde" id="serializing-and-deserializing-arbitrary-data-into-and-from-jsvalue-with-serde">Serializing and Deserializing Arbitrary Data Into and From <code>JsValue</code> with Serde</a></h1>
|
|
<p>It's possible to pass arbirtrary data from Rust to JavaScript by serializing it
|
|
to JSON with <a href="https://github.com/serde-rs/serde">Serde</a>. <code>wasm-bindgen</code> includes
|
|
the <code>JsValue</code> type, which streamlines serializing and deserializing.</p>
|
|
<h2><a class="header" href="#enable-the-serde-serialize-feature" id="enable-the-serde-serialize-feature">Enable the <code>"serde-serialize"</code> Feature</a></h2>
|
|
<p>To enable the <code>"serde-serialize"</code> feature, do two things in <code>Cargo.toml</code>:</p>
|
|
<ol>
|
|
<li>Add the <code>serde</code> and <code>serde_derive</code> crates to <code>[dependencies]</code>.</li>
|
|
<li>Add <code>features = ["serde-serialize"]</code> to the existing <code>wasm-bindgen</code>
|
|
dependency.</li>
|
|
</ol>
|
|
<pre><code class="language-toml">[dependencies]
|
|
serde = "^1.0.59"
|
|
serde_derive = "^1.0.59"
|
|
|
|
[dependencies.wasm-bindgen]
|
|
version = "^0.2"
|
|
features = ["serde-serialize"]
|
|
</code></pre>
|
|
<h2><a class="header" href="#import-serdes-custom-derive-macros" id="import-serdes-custom-derive-macros">Import Serde's Custom-Derive Macros</a></h2>
|
|
<p>In your top-level Rust file (e.g. <code>lib.rs</code> or <code>main.rs</code>), enable the <code>Serialize</code>
|
|
and <code>Deserialize</code> custom-derive macros:</p>
|
|
<pre><pre class="playpen"><code class="language-rust">
|
|
# #![allow(unused_variables)]
|
|
#fn main() {
|
|
#[macro_use]
|
|
extern crate serde_derive;
|
|
#}</code></pre></pre>
|
|
<h2><a class="header" href="#derive-the-serialize-and-deserialize-traits" id="derive-the-serialize-and-deserialize-traits">Derive the <code>Serialize</code> and <code>Deserialize</code> Traits</a></h2>
|
|
<p>Add <code>#[derive(Serialize, Deserialize)]</code> to your type. All of your type's
|
|
members must also be supported by Serde, i.e. their types must also implement
|
|
the <code>Serialize</code> and <code>Deserialize</code> traits.</p>
|
|
<p>For example, let's say we'd like to pass this <code>struct</code> to JavaScript; doing so
|
|
is not possible in <code>wasm-bindgen</code> normally due to the use of <code>HashMap</code>s, arrays,
|
|
and nested <code>Vec</code>s. None of those types are supported for sending across the wasm
|
|
ABI naively, but all of them implement Serde's <code>Serialize</code> and <code>Deserialize</code>.</p>
|
|
<p>Note that we do not need to use the <code>#[wasm_bindgen]</code> macro.</p>
|
|
<pre><pre class="playpen"><code class="language-rust">
|
|
# #![allow(unused_variables)]
|
|
#fn main() {
|
|
#[derive(Serialize)]
|
|
pub struct Example {
|
|
pub field1: HashMap<u32, String>,
|
|
pub field2: Vec<Vec<f32>>,
|
|
pub field3: [f32; 4],
|
|
}
|
|
#}</code></pre></pre>
|
|
<h2><a class="header" href="#send-it-to-javascript-with-jsvaluefrom_serde" id="send-it-to-javascript-with-jsvaluefrom_serde">Send it to JavaScript with <code>JsValue::from_serde</code></a></h2>
|
|
<p>Here's a function that will pass an <code>Example</code> to JavaScript by serializing it to
|
|
<code>JsValue</code>:</p>
|
|
<pre><pre class="playpen"><code class="language-rust">
|
|
# #![allow(unused_variables)]
|
|
#fn main() {
|
|
#[wasm_bindgen]
|
|
pub fn send_example_to_js() -> JsValue {
|
|
let mut field1 = HashMap::new();
|
|
field1.insert(0, String::from("ex"));
|
|
let example = Example {
|
|
field1,
|
|
field2: vec![vec![1., 2.], vec![3., 4.]],
|
|
field3: [1., 2., 3., 4.]
|
|
};
|
|
|
|
JsValue::from_serde(&example).unwrap()
|
|
}
|
|
#}</code></pre></pre>
|
|
<h2><a class="header" href="#receive-it-from-javascript-with-jsvalueinto_serde" id="receive-it-from-javascript-with-jsvalueinto_serde">Receive it from JavaScript with <code>JsValue::into_serde</code></a></h2>
|
|
<p>Here's a function that will receive a <code>JsValue</code> parameter from JavaScript and
|
|
then deserialize an <code>Example</code> from it:</p>
|
|
<pre><pre class="playpen"><code class="language-rust">
|
|
# #![allow(unused_variables)]
|
|
#fn main() {
|
|
#[wasm_bindgen]
|
|
pub fn receive_example_from_js(val: &JsValue) {
|
|
let example: Example = val.into_serde().unwrap();
|
|
...
|
|
}
|
|
#}</code></pre></pre>
|
|
<h2><a class="header" href="#javascript-usage" id="javascript-usage">JavaScript Usage</a></h2>
|
|
<p>In the <code>JsValue</code> that JavaScript gets, <code>field1</code> will be an <code>Object</code> (not a
|
|
JavaScript <code>Map</code>), <code>field2</code> will be a JavaScript <code>Array</code> whose members are
|
|
<code>Array</code>s of numbers, and <code>field3</code> will be an <code>Array</code> of numbers.</p>
|
|
<pre><code class="language-js">import { send_example_to_js, receive_example_from_js } from "example";
|
|
|
|
// Get the example object from wasm.
|
|
let example = send_example_to_js();
|
|
|
|
// Add another "Vec" element to the end of the "Vec<Vec<f32>>"
|
|
example.field2.push([5,6]);
|
|
|
|
// Send the example object back to wasm.
|
|
receive_example_from_js(example);
|
|
</code></pre>
|
|
<h2><a class="header" href="#an-alternative-approach-serde-wasm-bindgen" id="an-alternative-approach-serde-wasm-bindgen">An Alternative Approach: <code>serde-wasm-bindgen</code></a></h2>
|
|
<p><a href="https://github.com/cloudflare/serde-wasm-bindgen">The <code>serde-wasm-bindgen</code>
|
|
crate</a> serializes and
|
|
deserializes Rust structures directly to <code>JsValue</code>s, without going through
|
|
temporary JSON stringification. This approach has both advantages and
|
|
disadvantages.</p>
|
|
<p>The primary advantage is smaller code size: going through JSON entrenches code
|
|
to stringify and parse floating point numbers, which is not a small amount of
|
|
code. It also supports more types than JSON does, such as <code>Map</code>, <code>Set</code>, and
|
|
array buffers.</p>
|
|
<p>There are two primary disadvantages. The first is that it is not always
|
|
compatible with the default JSON-based serialization. The second is that it
|
|
performs more calls back and forth between JS and Wasm, which has not been fully
|
|
optimized in all engines, meaning it can sometimes be a speed
|
|
regression. However, in other cases, it is a speed up over the JSON-based
|
|
stringification, so — as always — make sure to profile your own use
|
|
cases as necessary.</p>
|
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