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August 18, 2017 04:53
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AJAX Javascript loader for poor connections
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/* | |
[License] | |
MIT | |
[Purpose] | |
Also lets you verify the result content is valid or else it keeps retrying. | |
[Sample Usage] | |
getJsWithRetries("path/to/some.js", resp => resp.length === 100) | |
.then(() => { | |
console.success(`Succeeded`); | |
}) | |
.catch(() => { | |
console.error(`Failed`); | |
}); | |
*/ | |
function getJsWithRetries(url, isValidFn, | |
{ | |
retryTimes = 10, | |
onRetry = () => { } | |
}) { | |
return new Promise(function (resolve, reject) { | |
$.ajax({ | |
method: "GET", | |
url: url, | |
cache: false | |
}) | |
.done(onAjaxDone) | |
.error(onAjaxError); | |
function onAjaxDone(resp) { | |
if (isValidFn(resp)) { | |
appendAsScript(resp); | |
resolve(); | |
} else { | |
var safeOffset = Math.min(5000, resp.length); | |
retryAjax(resp ? `${resp.length}B response length: ${resp.substring(0, safeOffset)}` : null); | |
} | |
} | |
function onAjaxError(xhr, status, error) { | |
retryAjax(`code: '${xhr.status}' error: '${error}' status: '${status}'`); | |
} | |
function appendAsScript(text) { | |
const script = document.createElement('script'); | |
script.type = "text/javascript"; | |
const scriptContent = document.createTextNode(text); | |
script.appendChild(scriptContent); | |
} | |
function retryAjax(reason) { | |
if (retryTimes === 0) { | |
reject(); | |
return; | |
} | |
onRetry(retryTimes, reason); | |
retryTimes--; | |
getJsWithRetries(url, isValidFn, { retryTimes, onRetry }) | |
.then(resolve) | |
.catch(reject); | |
} | |
}); | |
} |
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