这两个循环有什么区别？ 为什么一个起作用而另一个不起作用？

Question

I want to know why is it that when I add a variable with a value of an empty string(") the loop works but when i remove it, the loop ...doesn't seem to loop within this function...

Here is the first loop:

function laugh(num) {
  var laugh = "ha";
  for (var i=0; i<=num; i++){
     laugh;
  }
  return laugh + "!";
}
console.log(laugh(3)); 

And here is the second one:

function laugh(num) {
  var string = "";
  var laugh = "ha";
  for (var i=1; i<=num; i++){
     string += laugh;
  }
  return string + "!";
}
console.log(laugh(3));

The first returns "ha!" while the second returns the correct amount of ha's ...which is "hahaha!"

why does adding an empty string make it work? Beginner by the way...I really don't want to move on to the next lesson until I have fully understood what is going on. Thanks so much!

Answer 1

That is because all you're doing in the first loop is a statement:

laugh;
//Equivalent to
"ha";

In the second loop, you are concatenating a new string to string :

string += laugh;

You need to do this concatenation otherwise it will only return ha! :

 function laugh(num) { var laugh = "ha"; for (var i = 0; i <= num; i++) { laugh += "ha"; } return laugh + "!"; } console.log(laugh(3));