For循环不适合函数

For loop does not work appropriate for the function

本文关键字：函数 不适合 循环 For      更新时间：2023-09-26

for循环包含一个函数，该函数通过checkPort函数指定端口是打开还是关闭。

var IPAdress = '192.168'; //Local area network to scan (this is rough)
var Portadd = 80; 
var Newip;
var i=0;
var j=0;
//scan over a range of IP addresses and execute a function each time the port is shown to be open.
for(i=0; i <= 1; i++){
for(j=0; j <= 3; j++){
Newip = IPAdress+'.'+i+'.'+j;
checkPort(Portadd, Newip, function(error, status, host, port) {
// Status should be 'open' since the HTTP server is listening on that port
if(status == "open"){
        console.log("IP" , Newip, "on port" , Portadd, "is open");
    }
else if(status == "closed"){
        console.log("IP" , Newip, "on port" , Portadd, "is closed");
    }
});
console.log(Newip);
}
}

，结果如下:

192.168.0.0
192.168.0.1
192.168.0.2
192.168.0.3
192.168.1.0
192.168.1.1
192.168.1.2
192.168.1.3
IP 192.168.1.3 on port 80 is closed
IP 192.168.1.3 on port 80 is closed
IP 192.168.1.3 on port 80 is closed
IP 192.168.1.3 on port 80 is closed
IP 192.168.1.3 on port 80 is closed
IP 192.168.1.3 on port 80 is closed
IP 192.168.1.3 on port 80 is closed
IP 192.168.1.3 on port 80 is closed

因为打印出来的NewIp工作正常，所以我期望结果是这样的:

IP 192.168.0.0 on port 80 is closed
IP 192.168.0.1 on port 80 is closed
IP 192.168.0.2 on port 80 is closed
IP 192.168.0.3 on port 80 is closed
IP 192.168.1.0 on port 80 is closed
IP 192.168.1.1 on port 80 is closed
IP 192.168.1.2 on port 80 is closed
IP 192.168.1.3 on port 80 is closed

有没有人知道为什么在实际结果部分会显示ip ?

checkPort使用稍后执行的回调函数，到执行时，变量NewIP中的所有IP地址都已更改。

所以结果是回调函数打印NewIP的最后一个值，因为它引用了这个值

你有两个选择:

  • 您可以使用传递给回调函数的参数host代替。
  • 通过改变var Newip = IPAdress+'.'+i+'.'+j;在内部for循环中定义var NewIP。这将创建一个作用域为回调函数的变量。

更改为:

checkPort(Portadd, Newip, function(error, status, host, port) {
    // Status should be 'open' since the HTTP server is listening on that port
    if(status == "open"){
            console.log("IP" , host, "on port" , port, "is open");
    }
    else if(status == "closed"){
            console.log("IP" , host, "on port" , port, "is closed");
    }
});

你不能传递" parent "变量到回调函数，特别是你有host和port输入参数

192.168.X范围内ip地址的完整示例。Y for X in [0,1,2] and Y in [0,1,2,3,4]:

var IPAdress = '192.168'; //Local area network to scan (this is rough)
var Portadd = 80; 
var i=0;
var j=0;
//scan over a range of IP addresses and execute a function each time the port is shown to be open.
for(i=0; i <= 2; i++){
    for(j=0; j <= 4; j++){
        var Newip = IPAdress + '.' + i + '.' + j;
        checkPort(Portadd, Newip, function(error, status, host, port) {
            // Status should be 'open' since the HTTP server is listening on that port
            if(status == "open"){
                console.log("IP" , host, "on port" , port, "is open");
            }else if(status == "closed"){
                console.log("IP" , host, "on port" , port, "is closed");
            }
        });
        console.log(Newip);
    }
}
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