如何识别检测rel =“prefetch”

Question

根据caniuse.com资源prefteching <link rel="prefetch" href="some-resource" />仅适用于某些浏览器。

如何在JavaScript中检测此功能？在下面的示例中，如何获得isPrefecthSupported的值

if(isPrefecthSupported) {
    let link = document.createElement('link');
    link.setAttribute('rel', 'prefetch');
    link.setAttribute('href', url);
    link.setAttribute('disabled', true);
    document.querySelector('head').appendChild(link);
} else {
   //try something else...
}

Answer 1

我终于设法检测它了。有边缘情况（当不支持DomTokenList.supports时）但你可以这样做：

var support = function support(feature){
    var tokenList;
    var fakeLink = document.createElement('link');
    try {
        if(fakeLink.relList && _.isFunction(fakeLink.relList.supports)){
            return  fakeLink.relList.supports(feature);
        }
    } catch(err){
        return false;
    }
};
var isPrefetchSupported = support('prefetch');
var isPreloadSupported = support('preload');