什么意思是“？” 用Javascript？

Question

Can anyone explain me this line of code and why we use the '?' in javascript?

return n > 0 ? ninja.yell(n-1) + "a" : "hiy"; 

Answer 1

This is a ternary operator which also present in other programming languages:

return n > 0 ? ninja.yell(n-1) + "a" : "hiy";
       ^^        ^^                     ^^
 if condition     if true               if false(else)

The above statement is equivalent to below:

if(n>0) {
   return ninja.yell(n-1) + "a";
} else {
   return "hiy";
}

For more read this tutorial .

Answer 2

The question mark is actually called Ternary Operator , usually in programming laguages it is used for a one line if statement and it has the following construct:

condition ? return if condition is True : return if condition is False

Think the ternary operator as " then " and the " : " as else . So your code will be:

return if( n > 0) then ninja.yell(n-1) + "a" else "hiy";

Hope you get it now!