Mathematical Operator over Boolean values in JavaScript

Question

Can someone explain what will be the order of execution of following JavaScript Code:

(true + false) > 2 + true

I understand using + operator over two Boolean values returns the result as 0,1 or 2 depending upon the values being provided.

I interpreted output of above code as 1 by breaking the execution in following order:

1) (true + false) // Outputs : 1
2) 1 > 2 // Outputs : false
3) false + true //Outputs : 1

But the actual result is:

false

Can anyone correct my understanding if am interpreting the code in wrong way.

Suren Srapyan · Accepted Answer · 2018-03-12 09:51:46Z

2

Your 2nd point is not correct.

1) (true + false) outputs - 1
2) (2 + true) - outputs 3
3) 1 > 3 - outputs false

You can check this using functions

(true + false) > 2 + true

function f1() {
  const cond = true + false;
  console.log(cond);
  return cond;
}

function f2() {
  const cond = 2 + true;
  console.log(cond);
  return cond;
}

console.log(f1() > f2());

If you want to compare with 2 then add true, you must to wrap into the parentheses

((true + false) > 2) + true

answered Mar 12, 2018 at 9:51

Suren Srapyan

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2 Comments

Manish Over a year ago

So you mean first both + operator will be executed then comparison will take place?

Suren Srapyan Over a year ago

Yes, for the first example. The second will work inside parentheses than + true

Nina Scholz · Accepted Answer · 2018-03-12 10:03:24Z

1

What you have is a question of operator precedence, of three parts,

( ... ) grouping with the highest precedence of 20,
+ adition with precedence of 13, and
> greater than (here) with the lowest precendece of 11.

That means the operators with higer precedence are evaluated first and the comes the once with lower precedence.

(true + false) > 2 + true
(true + false)             -> 1
                 2 + true  -> 3

             1 > 3         -> false

answered Mar 12, 2018 at 10:03

Nina Scholz

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