Javascript中的递归函数返回未定义

Question

function right(a,b){ 
if( a > b) { 
  console.log(b+1);
  return b +1 ; } 
else 
{ 
  right(a +=1,b);
  console.log(a); } 

}

When I call this function it returns undefined. right(5,10) // undefined. Can anyone one help me why when the variable b is declared and has the value.

Answer 1

Basically you need to return on the else part something as well.

function right(a,b){ 
    if( a > b) { 
        console.log(b + 1); 
        return b + 1;
    } else {
       console.log(a + 1);
       return right(a + 1, b);
       // ^^^
    } 
}