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November 28, 2016 20:24
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<bc-require>: Basecamp 3's lazy JavaScript loader
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| BC.registerElement "bc-require", | |
| createdCallback: -> | |
| @setAttribute("pending", "") | |
| attachedCallback: -> | |
| BC.ready => | |
| if Loader.find(@script)?.loaded | |
| @activate() | |
| else | |
| @deactivate() | |
| Loader.load(@script).then => @activate() | |
| script: | |
| get: -> | |
| @getAttribute("script") | |
| deactivate: -> | |
| @placeholderStyle = getPlaceholderStyle(this, "width", "height") | |
| @style[key] = value for key, value of @placeholderStyle | |
| @pendingFragment = document.createDocumentFragment() | |
| @pendingFragment.appendChild(child) for child in [@childNodes...] | |
| activate: -> | |
| @removeAttribute("pending") | |
| if @pendingFragment? | |
| @appendChild(@pendingFragment) | |
| delete @pendingFragment | |
| @style[key] = null for key of @placeholderStyle | |
| delete @placeholderStyle | |
| BC.triggerEvent(this, "bc-require-activate") | |
| getPlaceholderStyle = (element, styles...) -> | |
| computedStyle = getComputedStyle(element) | |
| result = {} | |
| result[key] = computedStyle[key] for key in styles | |
| result | |
| class Loader | |
| @loaders: {} | |
| @find: (script) -> | |
| @loaders[script] | |
| @create: (script) -> | |
| @loaders[script] = new this script | |
| @load: (script) -> | |
| @find(script) ? @create(script) | |
| constructor: (@script) -> | |
| @promise = new Promise (@resolve, @reject) => | |
| @load() | |
| then: (callback) -> | |
| @promise.then(callback) | |
| load: -> | |
| link = @findLinkElement() | |
| script = document.createElement("script") | |
| script.src = link.href | |
| script.onload = @didLoad | |
| link.parentNode.insertBefore(script, link) | |
| didLoad: => | |
| @loaded = true | |
| @resolve() | |
| findLinkElement: -> | |
| document.head.querySelector("link[rel=subresource][data-script='#{@script}']") |
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| <head> | |
| <link rel="subresource" href="[URL for rich_text.js]" data-script="rich_text" data-turbolinks-track="reload" /> | |
| </head> | |
| <body> | |
| <bc-require script="rich_text"> | |
| This content will be removed from the DOM until rich_text.js loads | |
| </bc-require> | |
| </body> |
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BC.registerElementis a helper aroundDocument.registerElement()