Ajax request global configuration that encapsulates jQuery_jquery

// ajax request parameters
var ajaxSettings = function(opt) {
var url = opt.url;
var href = location.href;
// Determine whether there is a cross-domain request
var requestType = 'jsonp';
If (url.indexOf(location.host) > -1)
        requestType = 'json';
requestType = opt.dataType || requestType;
// Whether to request asynchronously
var async = (opt.async === undefined ? true : opt.async);
Return {
  url: url,
async: async,
         type: opt.type || 'get',
dataType: requestType,
cache: false,
data: opt.data,
Success: function(data, textStatus, xhr) {
               /*
*If dataType is json, how to determine whether the returned data is in json format? If not, convert it
* Common format of successful data
                 *                                             “code”: 200,
“data”: [],
                                                                                                                                                               *                                               * Data returned on failure
                 *                                             “code”: 200,
"info": 'error',
“success”: false // Failed                  *                                                               */
If((requestType === 'json' || requestType === "jsonp") && typeof(data) === "string") {
                  data = JSON.parse(data);
            }
                 if(data.success) {
                     opt.success(data);
            }

if(opt.error) {
                    opt.error(data);
            }

        },
        error: function(xhr, status, handler) {
            if (opt.error)
                opt.error();
        }
    };
};
function unescapeEntity(str) {
    var reg = /&(?:nbsp|#160|lt|#60|gt|62|amp|#38|quot|#34|cent|#162|pound|#163|yen|#165|euro|#8364|sect|#167|copy|#169|reg|#174|trade|#8482|times|#215|divide|#247);/g,
        entity = {
        ' '   : ' ',
        ' '   : ' ',
        '<'     : '<',
        '<'    : '<',
        '>'     : '>',
        '&62;'     : '>',
        '&'    : '&',
        '&'    : '&',
        '"'   : '"',
        '"'    : '"',
        '¢'   : '￠',
        '¢'   : '￠',
        '£'  : '£',
        '£'   : '£',
        '¥'    : '¥',
        '¥'   : '¥',
        '€'   : '?',
        '€'  : '?',
        '§'   : '§',
        '§'   : '§',
        '©'   : '©',
        '©'   : '©',
        '®'    : '®',
        '®'   : '®',
        '™'  : '™',
        '™'  : '™',
        '×'  : '×',
        '×'   : '×',
        '÷' : '÷',
        '÷'   : '÷'
    };
    if (str === null) {
        return '';
    }
    str = str.toString();
    return str.indexOf(';') < 0 ? str : str.replace(reg, function(chars) {
        return entity[chars];
    });
}
// 转换html的实体
$.ajaxSetup({
    global     : true,
    cache      : false,
    converters : {
        'text json' : function(response){
            return jQuery.parseJSON(unescapeEntity(response));
        }
    }
});
/*
*Ajax 请求权限异常
*   用户权限错误跳转登陆页
*   404错误跳转404页面
 */
$(document).ajaxComplete(function(evt, req, settings){
    if(req && req.responseJSON){
        var json = req.responseJSON;
        if(json.code === 403 && json.info === 'perm error' && !json.success){
            window.location.href = location.protocol '//' location.hostname;
            return;
        }
        if(json.code === 404 && !json.success) {
                 window.location.href = location.protocol '//' location.hostname '/404.html';
}
}
});
/*
*Ajax request error message
*Example: 500 error
*Return error message format
*{
* code: 500,
* info: System exception
*}
*/
$(document).ajaxError(function(evt, req, settings){
If(req && (req.status === 200||req.status === 0)){ return false; }
var msg = 'Error:';
If(req && req.responseJSON){
      var json = req.responseJSON;
          msg = json.code||'';
            msg = json.info||'System exception, please try again';
}else{
            msg = 'System exception, please try again';
}
alert(msg);
});

$.ajax(ajaxSettings({
url: '',
Data: ''
}))