Using SetTimeout & window.settimeout with parameters in a Javascript class (parameters can be objects)

Recently encountered a Javascript exam, which reads as follows:

Try to implement the Javascript code in the annotation section to add more anywhere else
Code (if not implemented, explain why it cannot be implemented):

var Obj = function (msg) ... {
this.msg = msg;
This.shout = function () ... {
alert (this.msg);
}

This.waitandshout = function () ... {
Perform the above shout method after five seconds
}
}

var testobj = new OBJ ("hello,world!");
Testobj.shout ();
Frankly, I didn't use settimeout/setinterval experience in Javascript, so I started off thinking it was impossible. But after careful deliberation, it can be realized. To step back, executing a paragraph every five seconds is very easy to implement. For example, without considering other factors, the function in the topic can be written as follows:

this. waitandshout = function () ... {
SetTimeout (' This.shout () ', 5000);
}
After running, anyone will realize that this variable is not found. But this is why, it is very soon to realize that Settimeout/setinterval is actually a method of window object, so can also be written as Window.settimeout/window.setinterval, then the above this Shout () is very easy to understand why it cannot be performed because it actually calls Window.shout ().

Knowing the cause is a lot easier to solve, as long as you bind the object to the Window object (I'm excited about the interesting object mechanism of Javascript). So, the above function makes a minor modification:

this. waitandshout = function () ... {
Window. OBJ = this;
SetTimeout (' Obj.shout () ', 5000);
}
That's it. As a matter of fact

SetTimeout (' Obj.shout () ', 5000);
Equivalent to

Window.settimeout (' window. Obj.shout () ', 5000);
Also, before I thought about saving an object as an array, and then referencing the call, the code was as follows:

function objectclass (property) ... {
This.property = property;
This.id = objectclass.cnt;
objectclass.objects[objectclass.cnt++] = this;
This.method = Objectclass_method;
}

objectclass.cnt = 0;
objectclass.objects = new Array ();

function Objectclass_method () ... {
settimeout (' objectclass.objects[' + this.id + '].method (); ', 5000);
}

var obj1 = new objectclass (' Feelinglucky ');
Obj1.method ();
But personal feeling is still much clearer than the first of these methods.

PostScript, Javascript does seem to be a lot of places to be cautious, especially the object mechanism. As I said before, Javascript is no more complicated than other languages, but it's not as simple as you might think.

PS: After the completion of this topic, Google found that other brothers have already solved this kind of problem, such as here and here, you can compare reference.


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Update, thanks to the Sheneyan brothers reminders, there is another way is through the Closure (closure) to implement, the code is as follows:

var Obj = function (msg) ... {
this.msg = msg;
This.shout = function () ... {
alert (this.msg);
This.waitandshout ();
}