封装

    function ajax() {
        var ajaxData = {
            type: arguments[0].type || "GET",
            url: arguments[0].url || "",
            async: arguments[0].async || "true",
            data: arguments[0].data || null,
            dataType: arguments[0].dataType || "text",
            contentType: arguments[0].contentType || "application/x-www-form-urlencoded",
            beforeSend: arguments[0].beforeSend || function () { },
            success: arguments[0].success || function () { },
            error: arguments[0].error || function () { }
        }
        ajaxData.beforeSend()
        var xhr = createxmlHttpRequest();
        xhr.responseType = ajaxData.dataType;
        xhr.open(ajaxData.type, ajaxData.url, ajaxData.async);
        xhr.setRequestHeader("Content-Type", ajaxData.contentType);
        xhr.send(convertData(ajaxData.data));
        xhr.onreadystatechange = function () {
            if (xhr.readyState == 4) {
                if (xhr.status == 200) {
                    ajaxData.success(xhr.response)
                } else {
                    ajaxData.error()
                }
            }
        }
    }

    function createxmlHttpRequest() {
        if (window.ActiveXObject) {
            return new ActiveXObject("Microsoft.XMLHTTP");
        } else if (window.XMLHttpRequest) {
            return new XMLHttpRequest();
        }
    }

    function convertData(data) {
        if (typeof data === 'object') {
            var convertResult = "";
            for (var c in data) {
                convertResult += c + "=" + data[c] + "&";
            }
            convertResult = convertResult.substring(0, convertResult.length - 1)
            return convertResult;
        } else {
            return data;
        }
    }

使用

     ajax({
            type: "POST",
            url: "http://127.0.0.1",
            dataType: "json",
            data: data,
            beforeSend: function () {
                //some js code 
            },
            success: function (msg) {
                console.log(msg)
            },
            error: function () {
                console.log("error")
            }
        })