285 lines
7.5 KiB
HTML
285 lines
7.5 KiB
HTML
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<title>Q.js cheatsheet</title>
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<body>
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<div class='all'>
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<div class='site-header'>
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<div class='container'>
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This is <a href="."><em>Devhints.io cheatsheets</em></a> — a collection of cheatsheets I've written.
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"description": "The one-page guide to Q.js: usage, examples, links, snippets, and more."
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"name": "JavaScript libraries"
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<div class='post-list -single -cheatsheet'>
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<div class='post-item'>
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<div class='post-headline -cheatsheet'>
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<p class='prelude'><span></span></p>
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<h1><span>Q.js</span></h1>
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<div class='pubbox'>
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<div class='HeadlinePub' role='complementary'>
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<script async src='https://pubsrv.devhints.io/carbon.js?serve=CE7IK5QM&placement=devhintsio&cd=pubsrv.devhints.io/s' id="_carbonads_js"></script>
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<span class='placeholder -one'></span>
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<span class='placeholder -two'></span>
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<span class='placeholder -three'></span>
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<span class='placeholder -four'></span>
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</div>
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</div>
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</div>
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<div class='post-content -cheatsheet'>
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<h3 id="creating-promises-qpromise">Creating promises (Q.promise)</h3>
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<pre><code>Q.promise (ok, fail) =>
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asyncFunction ->
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if error
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fail new Error("Failure")
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else
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ok(data)
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</code></pre>
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<h3 id="for-arrays">For arrays</h3>
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<pre><code>promises = [saveDisk(), saveCloud()]
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# When all succeeds, or *at least one* error
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Q.all(promises).done ->
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alert "Saved"
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# Same, but get the values
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Q.all(promises).spread (a, b) ->
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alert "Result A:" + a
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alert "Result B:" + b
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# When all either succeeds or errors
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Q.allSettled(promises).done -> ...
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</code></pre>
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<h3 id="creating-promises-from-node">Creating promises from Node</h3>
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<pre><code># Works like .call() or .apply()
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Q.nfcall(FS.readFile, 'foo.txt', 'utf-8')
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.then -> ...
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Q.nfapply(FS.readFile, ['foo.txt', 'utf-8'])
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.then -> ...
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Q.npost(FS, 'readFile', ['foo.txt, 'utf-8'])
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.then -> ...
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Q.npost(FS, 'readFile', 'foo.txt, 'utf-8')
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.then -> ...
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readFile = Q.denodeify(FS.readFile)
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readFile('foo.txt').then -> ...
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</code></pre>
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<h3 id="promises-to-node-async">Promises to Node async</h3>
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<pre><code>createUser = (next) ->
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promiseMaker()
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.nodeify(next)
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</code></pre>
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<h3 id="promise-sugars">Promise sugars</h3>
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<pre><code># Shortcut for .then(ok, fail, progress)
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promise
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.then (data) ->
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.catch (err) ->
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.progress (percent) ->
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</code></pre>
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<h3 id="try">Try</h3>
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<p>Q.try ->
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promise()</p>
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<p>.catch (e) ->
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console.error “Oh well”, e</p>
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<h3 id="reference">Reference</h3>
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<ul>
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<li>https://github.com/kriskowal/q/wiki/API-Reference</li>
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</ul>
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</div>
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<ul class="social-list ">
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<li class="facebook link hint--bottom" data-hint="Share on Facebook"><a href="https://www.facebook.com/sharer/sharer.php?u=https://devhints.io/qjs.html" target="share"><span class="text"></span></a></li>
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</ul>
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</div>
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</div>
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<div class="about-the-site">
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<div class="container">
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<p class='blurb'>
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<strong><a href=".">Devhints.io cheatsheets</a></strong> is a collection of cheatsheets I've written over the years.
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Suggestions and corrections? <a href='https://github.com/rstacruz/cheatsheets/issues/907'>Send them in</a>.
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<i class='fleuron'></i>
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I'm <a href="http://ricostacruz.com">Rico Sta. Cruz</a>.
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Check out my <a href="http://ricostacruz.com/til">Today I learned blog</a> for more.
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</p>
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<p class='back'>
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<a class='big-button -back -slim' href='.#toc'></a>
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</p>
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<p>
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</p>
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</div>
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</div>
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<script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/8.5/highlight.min.js"></script>
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