原生ajax封装

        var params = {
            word1: ‘deep‘,
            word2: ‘dark‘,
            word3: ‘develop‘
        }
        ajax({
            method: ‘post‘,
            url: ‘http://127.0.0.1:8081/post_test‘,
            data: params,
            async: true,
            success: function (data) {
                console.log(data)
            },
            error: function (err) {
                console.log(err)
            }
        })

function ajax(obj) {
        //设置async默认为true
        if(obj.async==null){
            obj.async = true;
        }
        
        //callback函数利用闭包访问obj和xhr对象
        function callback() {
            if (xhr.status == 200) {
                obj.success(xhr.responseText)
            } else {
                obj.error("error" + xhr.status)
            }
        }
        var xhr = new XMLHttpRequest();
        xhr.onreadystatechange = function () {
            if (xhr.readyState == 4) {
                callback();//利用闭包调用callback
            }
        };

        if (obj.data != null) {
            var uri = ‘?‘;
            for (let i in obj.data) {
                uri += i + "=" + obj.data[i] + "&";
            }
            uri = uri.substring(0, uri.length - 1);
        } else {
            var uri = ‘‘;
        }
        //get请求
        if (obj.method == ‘get‘) {
            xhr.open("get", obj.url + uri, obj.async);
            xhr.send();
        }
        //post请求
        else if (obj.method == ‘post‘) {
            uri = uri.substring(1,uri.length);
            xhr.open(obj.method, obj.url, obj.async);
            xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
            xhr.send(uri);
        }

    }

var express = require(‘express‘);
var app = express();
var bodyParser = require(‘body-parser‘);
var urlencodedParser = bodyParser.urlencoded({extended:false})
//设置跨域访问
app.all(‘*‘, function(req, res, next) {
    res.header("Access-Control-Allow-Origin", "*");
    res.header("Access-Control-Allow-Headers", "X-Requested-With");
    res.header("Access-Control-Allow-Methods","PUT,POST,GET,DELETE,OPTIONS");
    res.header("X-Powered-By",‘ 3.2.1‘)
    res.header("Content-Type", "application/json;charset=utf-8");
    next();
});
app.get(‘/get_test‘,function(req,res){
    var response = {
        word1: req.query.word1,
        word2: req.query.word2,
        word3: req.query.word3
    }
    res.send(response)
})

app.post(‘/post_test‘,urlencodedParser,function(req,res){
    var response = {
        word1: req.body.word1,
        word2: req.body.word2,
        word3: req.body.word3
    }
    res.send(response)
})

app.listen(8081)