为什么回来； 不停止功能？

Question

Here is the code I simplified, but the nature of the problem is the same:

var counter=0;

function test(){
    window.onclick="return;";
    t.value=counter;
    counter++;
    setTimeout(test,1000);
}

t=document.createElement("textarea");
document.body.insertBefore(t, document.body.firstChild);
test();

Sets up a timer, however, as you can see, the clock does not stop (ie function exits) after I clicked the window. So where is the problem?

Edit : The motivation of this question comes from: Early exit from function?

Edit^2 : Then there is noway to make 'onlick' trigger the returning value of test()? (ie equivalent of asking whether a function can return as its super-function)

Answer 1

That function has long since exited when you're trying to call return . JavaScript isn't going to throw itself into a time machine and prevent the setTimer call from being executed. It's too late for that.

What you need to do is cancel the timer, and in order to do that you have to save a handle to it:

var counter = 0;
var timer;

function test(){
    window.onclick = function() {
      if (timer) { clearTimeout(timer) }
    }

    t.value=counter;
    counter++;
    timer = setTimeout(test,1000);
}

Answer 2

Every ten minutes, you tell your wife "if you see a postman, do nothing.". Unsurprisingly, when she sees a postman, she does nothing.

Basically, what you're doing is identical, but less secure, way of writing this:

window.onclick = function() {
  return;
}

ie when a click is detected, it executes a function that does nothing but return. It has nothing to do with the function test .

Answer 3

In the statement:

window.onclick="return;";

the string "return;" is assigned to the window.onclick property, which will replace the current value (whatever that might be).

If your intention was to end execution of the test function, then a return statement is required:

return;

The return keyword must appear as the start of a statement, it can't be assigned.