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December 18, 2015 19:10
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A non-blocking require function which dynamically loads javascript files synchronously into the DOM
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| function require(scripts, callback) { | |
| var i, xhr, head, events = { | |
| onload: function(e) { | |
| var tag = document.createElement('script') | |
| tag.textContent = xhr.responseText | |
| head.appendChild(tag) | |
| next() | |
| }, | |
| onerror: function(e, message) { | |
| console.error(`require script ${i+1} of ${scripts.length}: | |
| "${scripts[i].id}" could not load. ${message||''} | |
| require is ending prematurely.`) | |
| end(false) | |
| }, | |
| ontimeout: function(e) { | |
| events.error(e, 'Operation timeout.') | |
| } | |
| } | |
| function start() { | |
| head = document.getElementsByTagName('head')[0] | |
| if (!head) throw new ReferenceError('Missing <head> element') | |
| i = -1; xhr = new XMLHttpRequest(); xhr.timeout = 5000 | |
| Object.assign(xhr, events) | |
| next() | |
| } | |
| function next() { | |
| if (!scripts[++i]) { return end(true) } | |
| if (window[scripts[i].id]) { return next() } | |
| // replace default event if a matching event is found on script | |
| Object.keys(scripts[i]).forEach(key => { | |
| (events[key]) ? xhr[key] = scripts[i][key] : xhr[key] = events[key] | |
| }) | |
| xhr.open('GET', scripts[i].src, true) | |
| xhr.send() | |
| } | |
| function end(is_success) { | |
| if (is_success && callback) { callback() } | |
| } | |
| start() | |
| } |
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