node跨域问题

app.all("*",function(req,res,next){
    //设置允许跨域的域名，*代表允许任意域名跨域
    res.header("Access-Control-Allow-Origin","*");
    //允许的header类型
    res.header("Access-Control-Allow-Headers","content-type");
    //跨域允许的请求方式 
    res.header("Access-Control-Allow-Methods","DELETE,PUT,POST,GET,OPTIONS");
    if (req.method.toLowerCase() == ‘options‘)
        res.send(200);  //让options尝试请求快速结束
    else
        next();
})

app.all("*",function(req,res,next){
    //设置允许跨域的域名，*代表允许任意域名跨域
    res.header("Access-Control-Allow-Origin","http://www.zhangpeiyue.com");
    //允许的header类型
    res.header("Access-Control-Allow-Headers","content-type");
    //跨域允许的请求方式 
    res.header("Access-Control-Allow-Methods","DELETE,PUT,POST,GET,OPTIONS");
    if (req.method.toLowerCase() == ‘options‘)
        res.send(200);  //让options尝试请求快速结束
    else
        next();
}

app.all("*",function(req,res,next){
    if( req.headers.origin.toLowerCase() == "http://www.zhangpeiyue.com"
        || req.headers.origin.toLowerCase() =="http://127.0.0.1" ) {
        //设置允许跨域的域名，*代表允许任意域名跨域
        res.header("Access-Control-Allow-Origin", req.headers.origin);
    }
    //允许的header类型
    res.header("Access-Control-Allow-Headers", "content-type");
    //跨域允许的请求方式 
    res.header("Access-Control-Allow-Methods", "DELETE,PUT,POST,GET,OPTIONS");
    if (req.method.toLowerCase() == ‘options‘)
        res.send(200);  //让options尝试请求快速结束
    else
        next();    
}

//或者

app.all("*",function(req,res,next){
    var orginList=[
        "http://www.zhangpeiyue.com",
        "http://www.alibaba.com",
        "http://www.qq.com",
        "http://www.baidu.com"
    ]
    if(orginList.includes(req.headers.origin.toLowerCase())){
        //设置允许跨域的域名，*代表允许任意域名跨域
        res.header("Access-Control-Allow-Origin",req.headers.origin);
    }
    //允许的header类型
    res.header("Access-Control-Allow-Headers", "content-type");
    //跨域允许的请求方式
    res.header("Access-Control-Allow-Methods", "DELETE,PUT,POST,GET,OPTIONS");
    if (req.method.toLowerCase() == ‘options‘)
        res.send(200);  //让options尝试请求快速结束
    else
        next();
}