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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="API documentation for the Rust `future_to_promise` fn in crate `wasm_bindgen_futures`."><meta name="keywords" content="rust, rustlang, rust-lang, future_to_promise"><title>wasm_bindgen_futures::future_to_promise - Rust</title><link rel="stylesheet" type="text/css" href="../normalize.css"><link rel="stylesheet" type="text/css" href="../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../dark.css"><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><script src="../storage.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="shortcut icon" href="../favicon.ico"><style type="text/css">#crate-search{background-image:url("../down-arrow.svg");}</style></head><body class="rustdoc fn"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">&#9776;</div><a href='../wasm_bindgen_futures/index.html'><div class='logo-container'><img src='../rust-logo.png' alt='logo'></div></a><div class="sidebar-elems"><p class='location'><a href='index.html'>wasm_bindgen_futures</a></p><script>window.sidebarCurrent = {name: 'future_to_promise', ty: 'fn', relpath: ''};</script><script defer src="sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../theme.js"></script><nav class="sub"><form class="search-form"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" disabled autocomplete="off" spellcheck="false" placeholder="Click or press S to search, ? for more options…" type="search"></div><a id="settings-menu" href="../settings.html"><img src="../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='out-of-band'><span id='render-detail'><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class='inner'>&#x2212;</span>]</a></span><a class='srclink' href='../src/wasm_bindgen_futures/lib.rs.html#207-227' title='goto source code'>[src]</a></span><span class='in-band'>Function <a href='index.html'>wasm_bindgen_futures</a>::<wbr><a class="fn" href=''>future_to_promise</a></span></h1><pre class='rust fn'>pub fn future_to_promise&lt;F&gt;(future: F) -&gt; <a class="struct" href="../js_sys/struct.Promise.html" title="struct js_sys::Promise">Promise</a> <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/future/future/trait.Future.html" title="trait core::future::future::Future">Future</a>&lt;Output = <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="struct" href="../wasm_bindgen/struct.JsValue.html" title="struct wasm_bindgen::JsValue">JsValue</a>, <a class="struct" href="../wasm_bindgen/struct.JsValue.html" title="struct wasm_bindgen::JsValue">JsValue</a>&gt;&gt; + 'static,&nbsp;</span></pre><div class='docblock'><p>Converts a Rust <code>Future</code> into a JavaScript <code>Promise</code>.</p>
<p>This function will take any future in Rust and schedule it to be executed,
returning a JavaScript <code>Promise</code> which can then be passed to JavaScript.</p>
<p>The <code>future</code> must be <code>'static</code> because it will be scheduled to run in the
background and cannot contain any stack references.</p>
<p>The returned <code>Promise</code> will be resolved or rejected when the future completes,
depending on whether it finishes with <code>Ok</code> or <code>Err</code>.</p>
<h1 id="panics" class="section-header"><a href="#panics">Panics</a></h1>
<p>Note that in wasm panics are currently translated to aborts, but &quot;abort&quot; in
this case means that a JavaScript exception is thrown. The wasm module is
still usable (likely erroneously) after Rust panics.</p>
<p>If the <code>future</code> provided panics then the returned <code>Promise</code> <strong>will not
resolve</strong>. Instead it will be a leaked promise. This is an unfortunate
limitation of wasm currently that's hoped to be fixed one day!</p>
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