ReferenceError: plus is not defined

Developed with uni-app, I want to get the mac address of the machine, but I found a piece of code from the Internet as follows

var net = plus.android.importClass("java.net.NetworkInterface")  
var wl0 = net.getByName('wlan0')  
var macByte = wl0.getHardwareAddress()  
var str = ''  
//下面这段代码来自网络  
for (var i = 0; i < macByte.length; i++) {
    
      
    var tmp = "";  
    var num = macByte[i];  
    if (num < 0) {
    
            
      tmp =(255+num+1).toString(16);  
    } else {
    
      
      tmp = num.toString(16);  
    }  
    if (tmp.length == 1) {
    
      
      tmp = "0" + tmp;  
    }  
    str += tmp;  
}  
console.log('mac', str)

Running it directly gives an error

Says plus is not defined.
This is because it runs directly into an ordinary browser, and ordinary browsers do not have a plus environment.

Connect directly to our mobile phone through USB and run without error!
And also get the correct mac address