my problem here that i don't understand how does the method called "objectchanger" works here is the source
function test()
{
this.value=5;
}
test.prototype.Add=function()
{
this.value++;
};
var obj = new test();
obj.Add();
alert(obj.value);
function objectchanger(fnc, obj)
{
fnc.call(obj);
//obj.fnc(); >> without this line of code it works fine but why?????
//why i don't need to write this code --
}
objectchanger(obj.Add, obj);
alert(obj.value); // the value is now 7
call is a method on the Function object. It calls a function with the passed-in object as the this value in the function. See the MDN docs on call.
So when objectchanger calls fnc.call(obj), it is calling test.prototype.Add.call(obj), which is the same as calling obj.Add().
When the "this" object is accessed within a javascript function, it takes it from the current executing context. By passing the "obj" in the call method, the "this" object within the function is set to the passed in object.
