Promise实战AJAX封装

var url = 'xxx';
// 封装一个get请求的方法
function request(url){
    return new Promise(function(resolve,reject){
        var XHR = new XMLHttpRequest();
        XHR.open('GET',url,true);
        XHR.send();
        XHR.onreadystatechange = function(){
            if(XHR.readyState==4 && XHR.status == 200){
                try{
                    var response = JSON.parse(XHR.responseText);
                    resolve(response)
                } catch(e){
                    reject(e);
                }
            }else{
                reject(new Error(XHR.statusText))
            }
        }

    })

}


request(url).then(function(res){
    console.log(res);
})
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