Eloquent JavaScript string concatenation syntax

Question

So this is from the Eloquent Javascript. I am trying to figure out why the return find has "(" + history + " + 5)" instead of "(history + 5)"???

Here is the code snippet:

function findSolution(target) {
  function find(start, history) {
    if (start == target)
      return history;
    else if (start > target)
      return null;
    else
      return find(start + 5, "(" + history + " + 5)") ||
             find(start * 3, "(" + history + " * 3)");
  }
  return find(1, "1");
}

The result:

console.log(findSolution(24));// → (((1 * 3) + 5) * 3)

Answer 1

So difference between "(" + history + " + 5)" and "(history + 5)" is

"(" + history + " + 5)"

"("  --> String
history  -->Number
"+5)"  -->String

Now if you combine these variable using + it will work like concatenation so "(" + history + "+5)" will give you (5+5) as String

But "(history + 5)" -->String will be like (history + 5) as history will be not a variable now its a string literal

Hope it will help