I introduced async.js into html, which needs to be used in es6. Some syntax, including async, works properly in Google, but in ie, errors are reported and lack of identification, and then async is not defined. Not even with the introduction of browser.min.js
I think the compatible ie9 written in https://github.com/caolan/async/ includes a higher version of

< html >
< head >

<title>Async Test</title>
<script type="text/javascript" src="async.js"></script>

< / head >

< body >

< script type= "text/javascript" > / / if the javascript here is changed to babel IE, it will not be reported that async is not defined, but Google code will not be executed

var test = [0, 1, 2];
async.forEachSeries(test, function(item, callback) {
    alert(item);
    setTimeout(callback, 1000);
}, function() {
    alert("all done");
});

< / script >
< script type= "text/babel" src= "browser.min.js" < / script >
< / body >
< / html >