关于js中的call的理解

function add (x, y) 
{ 
    console.log (x + y);
} 
function minus (x, y) 
{ 
    console.log (x - y); 
} 
add.call (minus , 1, 1);    //2

function myfunc1(){
    this.name = ‘Lee‘;
    this.myTxt = function(txt) {
        console.log( ‘i am‘,txt );
    }
}
 
function myfunc2(){
    myfunc1.call(this);
}
 
var myfunc3 = new myfunc2();
myfunc3.myTxt(‘Geing‘); // i am Geing
console.log (myfunc3.name);    // Lee