为什么这个简单的脚本永无休止？

Question

I have a simple JavaScript function, that looks like this:

 countDown(); function countDown() { var count = 10; document.write(count); if (count > 0) { count = count-1;; setTimeout(countDown, 1000); } } 

Why does the variable count never change? This function never ends . . .

Answer 1

Because the countDown() function sets the variable count to ten every time it is called. A slight scoping change will make the function behave as you might have intended.

var count = 10;

countDown();

function countDown() {

  document.write(count);

  if (count > 0) {
    count = count-1;;
    setTimeout(countDown, 1000);
  }

}