2 github 35883572 github_35883572 于 2016.09.08 23:19 提问

JS客户端检测,为什么总是Uncaught ReferenceError 错误?
 <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <script type="text/javascript">
        var client = function () {
            var engine = {
                //内核
                ie: 0,
                gecko: 0,
                webkit: 0,
                khtml:0,
                opera:0,
                //具体版本
                 ver: null
            };
            var browser = {
                //浏览器
                ie: 0,
                firefox: 0,
                safari: 0,
                konq: 0,
                opera: 0,
                chrome: 0,
                //具体的版本
                ver: null
            };
            return {
                engine: engine,
                browser: browser
            };
        }();
        var ua = navigator.userAgent;
        if (window.opener) {
            engine.ver =browser.ver = window.opera.version();
            engine.opera = browser.opera = parseFloat(engine.ver);
        }else if (/AppleWebKit\/(\S+)/.test(ua)) {
            engine.ver = RegExp["$1"];
            engine.webkit = parseFloat(engine.ver);
            //确定是Chrome还是Safari
            if (/Chrome\/(\S+)/.test(ua)) {
                browser.ver = RegExp["$1"];
                browser.chrome = parseFloat(browser.ver);
            }else{
                //近似地确定版本号
                var safariVersion = 1;
                if (engine.webkit < 100) {
                    safariVersion = 1;
                }else if (engine.webkit < 312) {
                    safariVersion = 1.2;
                }else if (engine.webkit < 412) {
                    safariVersion = 1.3;
                }else {
                    safariVersion = 2;
                }
                browser.safari = browser.ver = safariVersion;
            }
        }else if (/KHTML\/(\S+)/.test(ua) || /Konqueror\/([^;]+)/.test(ua)) {
            engine.ver = RegExp["$1"];
            engine.khtml = browser.konq = parseFloat(engine.ver);
        }else if (/rv:([^\)]+)\) Gecko\/\d{8}/.test(ua)) {
            engine.ver = RegExp["$1"];
            engine.khtml = browser.konq = parseFloat(browser.ver);
            //确定是不是Firefox
            if (/firefox\/(\S+)/.test(ua)) {
                browser.ver = RegExp["$1"];
                browser.firefox = parseFloat(browser.ver);
            }
        }else if (/MSIE ([^;]+)/.test(ua)) {
            engine.ver = browser.ver = RegExp["$1"];
            engine.ie = browser.ie = parseFloat(engine.ver);
        }
        if (client.engine.webkit){
            if(client.browser.chrome){
                alert("使用的浏览器是chrome")
            }else if(client.browser.safari){
                alert("浏览器是safari");
            }else if (client.engine.gecko){
                if (client.browser.firefox){
                    alert("浏览器是fir");
                }else {

                }
            }
        }
    </script>
</head>
<body>

</body>
</html>

总是出现Uncaught ReferenceError: engine is not defined;
为什么变量保存了调用函数后的值 engine 仍然是未定义的?

1个回答

qq_18128329
qq_18128329   2016.09.08 23:41
已采纳

首先,你声明了变量,是一个局部的变量,你让这个方法自调用了,并且 return 了出来,但是 你用一个变量 接住了这个return的值 如果想调用的话 需要 在调用的时候 增加 一个 client 来读取他的属性

修改后的代码 如下:

var client = function () {
var engine = {
//内核
ie: 0,
gecko: 0,
webkit: 0,
khtml:0,
opera:0,
//具体版本
ver: null
};
var browser = {
//浏览器
ie: 0,
firefox: 0,
safari: 0,
konq: 0,
opera: 0,
chrome: 0,
//具体的版本
ver: null
};
return {
engine: engine,
browser: browser
};
}();
var ua = navigator.userAgent;
if (window.opener) {
client.engine.ver =client.browser.ver = window.opera.version();
client.engine.opera = client.browser.opera = parseFloat(client.engine.ver);
}else if (/AppleWebKit\/(\S+)/.test(ua)) {
client.engine.ver = RegExp["$1"];
client.engine.webkit = parseFloat(client.engine.ver);
//确定是Chrome还是Safari
if (/Chrome\/(\S+)/.test(ua)) {
client.browser.ver = RegExp["$1"];
client.browser.chrome = parseFloat(client.browser.ver);
}else{
//近似地确定版本号
var safariVersion = 1;
if (engine.webkit < 100) {
safariVersion = 1;
}else if (engine.webkit < 312) {
safariVersion = 1.2;
}else if (engine.webkit < 412) {
safariVersion = 1.3;
}else {
safariVersion = 2;
}
client.browser.safari = client.browser.ver = safariVersion;
}
}else if (/KHTML\/(\S+)/.test(ua) || /Konqueror\/([^;]+)/.test(ua)) {
client.engine.ver = RegExp["$1"];
client.engine.khtml = client.browser.konq = parseFloat(client.engine.ver);
}else if (/rv:([^)]+)) Gecko\/\d{8}/.test(ua)) {
client.engine.ver = RegExp["$1"];
client.engine.khtml = client.browser.konq = parseFloat(client.browser.ver);
//确定是不是Firefox
if (/firefox\/(\S+)/.test(ua)) {
client.browser.ver = RegExp["$1"];
client.browser.firefox = parseFloat(client.browser.ver);
}
}else if (/MSIE ([^;]+)/.test(ua)) {
client.engine.ver = client.browser.ver = RegExp["$1"];
client.engine.ie = client.browser.ie = parseFloat(client.engine.ver);
}
if (client.engine.webkit){
if(client.browser.chrome){
alert("使用的浏览器是chrome")
}else if(client.browser.safari){
alert("浏览器是safari");
}else if (client.engine.gecko){
if (client.browser.firefox){
alert("浏览器是fir");
}else {

    }
  }
}

github_35883572
github_35883572 非常感谢
大约一年之前 回复
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