JavaScript Recursion exercise: Unexpected token else

Question

I have read about this error on other threads that mostly ask the user to remove semicolons. This seems to have no effect on my code.

function isEven(number){
if (number > 1)
  return isEven(number-2);
else if (number == 1)
  return false;
else if (number == 0)
  return true;
else if (number < 0)
  number *= -1
  return isEven(number);
else
  return "Error";
}

It seems that this line [number *= -1] is causing the error as if I remove it the code runs with no error except for negative numbers where the stack runs out of memory. What I'm trying to do is to make all numbers positive. Anyone that would like to help me out?

Solution

function isEven(number){
  if (number < 0){
    number *= -1
    return isEven(number);}
  else if (number > 1){
    return isEven(number-2);}
  else if (number == 1){
    return false;}
  else if (number == 0){
    return true;}
  else
    return "Error";
}

You need to put the code inside if/else inside {} brackets. You can omit them only if the body is a single line of code. See: w3schools.com/js/js_if_else.asp — K. Kirsz
– K. Kirsz, Commented Jul 12, 2017 at 7:37

Suresh Atta · Accepted Answer · 2017-07-12 07:42:34Z

1

Short answer: Wrap your codes with {}

if (){
 ..
 ..
}else {
 ..
 ..
}

Long answer :

else if (number < 0)
  number *= -1
  return isEven(number);

You are not using {} hence the very next line of the condition only considered as a statement belong to the else if and the later will be treated as general statements.

Since you have 2 lines of code in else if, the link broken there and your else became an orphan. That is the reason you seeing the error. Please wrap up your conditions in {}

function isEven(number){
if (number > 1){
  return isEven(number-2);
}
else if (number == 1){
  return false;
}
else if (number == 0){
  return true;
}
else if (number < 0){
  number *= -1
  return isEven(number);
}
else{
  return "Error";
}
}

Note: Not only to avoid this specific error but to avoid many other weird things always try to use {}. That makes everyones life easy.

edited Jul 12, 2017 at 7:42

answered Jul 12, 2017 at 7:36

Suresh Atta

122k38 gold badges206 silver badges315 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Patrick Bender Over a year ago

Thank you! Functional code posted above if anyone else want this information

prasanth · Accepted Answer · 2017-07-12 07:40:08Z

1

Problem is without curly brackets {}

Better you could add {}(curly brackets) on each if and else statement

function isEven(number) {
  if (number > 1) {
    return isEven(number - 2);
  } else if (number == 1) {
    return false;
  } else if (number == 0) {
    return true;
  } else if (number < 0) {
    number *= -1
    return isEven(number);
  } else {
    return "Error";
  }
}

console.log(isEven(-2))

answered Jul 12, 2017 at 7:40

prasanth

22.6k4 gold badges33 silver badges57 bronze badges

Comments

abhinav · Accepted Answer · 2017-07-12 07:40:44Z

1

The problem is that you are trying to execute 2 lines of code in the 3rd else if without wrapping it up in curly braces. By default only single line gets executed when you don't wrap up the block in curly braces.

function isEven(number){
  if (number > 1){
    return isEven(number-2);
  }
  else if (number == 1){
    return false;
  }
  else if (number == 0){
    return true;
  }
  else if (number < 0){
    number *= -1;
    return isEven(number);
  }
  else{
    return "Error";
  }
}

answered Jul 12, 2017 at 7:40

abhinav

6976 silver badges20 bronze badges

Collectives™ on Stack Overflow

JavaScript Recursion exercise: Unexpected token else

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related