[英]Polyfill for onload of script tag in <head>
I'm trying to lazy load javascript into the head with this function:我正在尝试使用此功能将 javascript 延迟加载到头部:
function bfLoadScripts(strPath) {
var r = false;
var scriptTag = document.createElement('script');
scriptTag.src = strPath;
scriptTag.type = 'text/javascript';
scriptTag.addEventListener('load',function() {
//alert('JS loaded');
r = true;
});
var headTag = document.getElementsByTagName('head')[0];
headTag.appendChild(scriptTag);
}
It works in FF (latest), Chrome (latest), IE 11 but not on Safari iOS 5.1 and Safari PC.它适用于 FF(最新)、Chrome(最新)、IE 11,但不适用于 Safari iOS 5.1 和 Safari PC。
I tried this before but it's also not supported in Safari:我之前尝试过,但 Safari 也不支持它:
scriptTag.onload = scriptTag.onreadystatechange = function() {
if ( !r && (!this.readyState || this.readyState == 'complete') ) {
r = true;
};
Is there a polyfill for the "onload" event? “onload”事件是否有polyfill? Or asked differently: Is there a total different way of doing this?或者换一种方式问:是否有完全不同的方式来做到这一点? Without overloading the whole process by using libraries, plugins etc.无需通过使用库、插件等重载整个过程。
This is my version, which works in IE 8 (TypeScript):这是我的版本,适用于 IE 8 (TypeScript):
type IE8ScriptReadyState = "loading" | "loaded";
interface IE8CompatibleScriptElement extends HTMLScriptElement
{
onreadystatechange: ()=> void;
readyState: IE8ScriptReadyState;
}
export function loadPolyfill(src): Promise<void>
{
return new Promise(function (resolve, reject)
{
let js = <IE8CompatibleScriptElement>document.createElement('script');
js.src = src;
if (!('onload' in js))
{
// @ts-ignore
js.onreadystatechange = function ()
{
if (js.readyState === 'loaded')
{
js.onreadystatechange = null;
resolve();
};
};
}
js.onload = function ()
{
js.onload = null;
resolve();
};
js.onerror = function ()
{
js.onerror = null;
reject(new Error('Failed to load script ' + src));
};
js.oncancel = function ()
{
js.oncancel = null;
reject(new Error('Cancelled loading of script ' + src));
};
if (document.head)
document.head.appendChild(js);
else
document.getElementsByTagName('head')[0].appendChild(js);
});
}
// loadScript("foo", function () { alert("hi"); });
// loadScript("/ts/myimport.js", function () { alert("hi"); });
function loadScript(src: string, done: (err?: Error) => void)
{
console.log(src);
let js = <IE8CompatibleScriptElement>document.createElement('script');
js.src = src;
if (!('onload' in js))
{
// @ts-ignore
js.onreadystatechange = function ()
{
if (js.readyState === 'loaded')
{
js.onreadystatechange = null;
if (done != null)
done();
};
};
}
js.onload = function ()
{
js.onload = null;
console.log("onload " + src);
if(done != null)
done();
};
js.onerror = function ()
{
js.onerror = null;
console.log("onerror " + src);
if (done != null)
done(new Error('Failed to load script ' + src));
};
//js.onloadend = function ()
//{
// alert("onerror");
// done(new Error('Failed to load script ' + src));
//};
js.oncancel = function ()
{
js.oncancel = null;
console.log("oncancel " + src);
if (done != null)
done(new Error('Cancelled loading of script ' + src));
};
if (document.head)
document.head.appendChild(js);
else
document.getElementsByTagName('head')[0].appendChild(js);
}
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