class AJAX {
    constructor() {
        // 请求基地址
        // this.baseUrl = "http://127.0.0.1:3000/api/json";
        this.baseUrl = "http://127.0.0.1:3000/api";
        this.http = new XMLHttpRequest();
    }

    /**
     * 
     * @param {*object} parmas 
     * {
     *   url: '', // 请求地址
     *   data : { page: 1, count: 15 } // 请求参数
     *   success: () => {}  // ajax成功后，回调拿回请求结果
     *   error: () => {} // ajax 失败后，回调拿回错误结果
     * }
     */
    get(parmas) {
        // 将data 参数转化为 ?key=value&key=value
        var str = ""
        for (const key in parmas.data) {
            str += `&${key}=${parmas.data[key]}`
        }
        str = str.replace("&", "?")

        this.http.open("GET", `${this.baseUrl}${parmas.url}${str}`);
        this.http.send();

        this.readyState(parmas.success, parmas.error)
    }

    post(parmas) {
        this.http.open("POST", `${this.baseUrl}${parmas.url}`);
        this.http.setRequestHeader('Content-type', 'application/json; charset="utf-8"');
        this.http.send(JSON.stringify(parmas.data));

        this.readyState(parmas.success, parmas.error)
    }


    put() { }
    delete() { }

    // 给 get post put delete 进行状态监听的封装
    readyState(success, error) {
        this.http.onreadystatechange = () => {
            if (this.http.readyState == 4) {
                if (this.http.status == 200) {
                    var data = JSON.parse(this.http.response);
                    success(data)
                } else {
                    error(this.http)
                }
            }
        }
    }
}

var http = new AJAX();