为什么我的服务器收不到ajax请求

Question

function ajax(options){
            //适配参数
            options = Object.assign({
                url: '',
                method: '',
                data: '',
                headers: {},
                async: true
            },options);
            //适配data属性
            if(typeof options.data !== "string"){
                let str = '';
                for(let key in options.data) {
                    str += `&${key} = ${options.data[key]}`;
                }
                options.data = str.slice(1);
            }
            if(options.method.toUpperCase() === 'GET') {
                options.url += '?' + options.data;
            }
            return new Promise((resolve, reject) => {
                let xhr;
                if(window.XMLHttpRequest) {
                    xhr = new XMLHttpRequest();
                }else if(window.ActiveXObject) {
                    xhr = new ActiveXObject();
                }else{
                    alert('浏览器版本过低')
                    return reject('浏览器不支持Ajax')
                }
            })
            xhr.onreadystatechange = function() {
                if(xhr.readyState === 4) {
                    if(xhr.status === 200 || xhr.status === 304) {
                        resolve(JSON.parse(xhr.responseText))
                    }else{
                        reject('请求失败')
                    }
                }
            }


            xhr.open(options.method, options.url, options.async);

            if(options.headers) {
                for(let key in options.headers) {
                    xhr.setRequestHeader(key, options.headers[key])
                }
            }

            xhr.send(options.data)

        }
      
            ajax({
                url:'/send',
                method: 'POST',
                data:{data}
            }).then(data => {
                console.log(11)
            })

Answer 1

把 xhr 用var声明再函数最顶部，别用let 声明再你所声明那个地方！