why wont my else if statement work? (the if and else work, but not the if else statement even though condition is met)

Question

I cannot get the if else statement to work, the if statement and the else statement works,
I test the if else statement with an input of 115, it doesnt work,
but if i put 135 the if statement works as it should.
I need help to fix the if else statement please!!

var start = button.addEventListener("click", function() {
  var lbs = input.value - 45 /*weight without the bar*/
  var add = 0

  var plates45 = 0
  var plates35 = 0

  while (lbs != add) {
    if ((add += 90) <= lbs) {
      plates45 += 2
      add += 90
      forty.innerHTML = "45lbs: " + plates45
    } else if ((add += 70) <= lbs) {
      plates35 += 2
      add += 70
      thirty.innerHTML = "35lbs: " + plates35
    } else {
      add = lbs /*to prevent infinte loop*/
    }
  }
})

<h1 id="header">Plate Helper</h1>

<div id="container1">
  <p id="weight">Weight</p>
  <input type="text" id="input">
</div>
<div id="blue">
  <button id="button">Calculate</button>
</div>

<div id="container2">
  <center>
    <p id="result">Plates Needed</p>
    <div id="forty">
      <p id="forty_plate">45lbs: </p>
    </div>
    <div id="thirty">
      <p id="thirty_plate">35lbs: </p>
    </div>
    <div id="twenty">
      <p id="twenty_plate">25lbs: </p>
    </div>
    <div id="ten">
      <p id="ten_plate">10lbs: </p>
    </div>
    <div id="five">
      <p id="five_plate">5lbs: </p>
    </div>
    <div id="two">
      <p id="two_plate">2.5lbs: </p>
    </div>
  </center>

I refresh the page before each test so i dont think the first if statement affects the condition for the if else statement

it's painful to read without the HTML part, you have to add it in your question https://stackoverflow.com/help/how-to-ask — Mister Jojo, Aug 07 '22 at 02:08
The `+=` in the `if` statements will increase the value of the `add` variable. So, within the first execution of the loop `add` will change from `0` (at the start) to `90` (at the `if` clause), and then to `180` (within the `if` when executing `add += 90`), and then to `250` (at the `else if` clause). To get the `else if` statements to execute, please try with `input.value` as a high number say 1045 (or at least above 296). And, kindly do include the HTML as noted by @MisterJojo above. — jsN00b, Aug 07 '22 at 02:11

Traveller · Answer 1 · 2022-08-07T02:21:41.653

0

The reason it doesn't work is the += operator in the if statements. The first one if ((add += 90) <= lbs){ first adds 90 to add, then checks if add is less than lbs. Then when it arrives at if ((add += 70) <= lbs){, add is already 90, so then it adds 70 (=160) and checks if it's less than lbs. The solution therefore would be to only add the amount (70 or 90) if the condition is true (i.e. replace += in if ((add += ... to + but leave the lines within the blocks the qay they are).

As a side note, an alternative way to break out of your loop in the else clause would be the break keyword.

P.s. You come from a Python background?

edited Aug 07 '22 at 02:21

answered Aug 07 '22 at 02:17

Traveller

604
6
16

yes i do come from a python background, i check the if else statement to work with a fresh page refresh with 115 as the input so the first if statement shouldnt affect the if else i dont think, i added the HTML for clarification – Yagami_Light Aug 07 '22 at 02:21
@Yagami_Light even if the contents of the first if block are not executed, the if statement itself is. So `plates45 +=2` is not executed, but `(add += 90) <= lbs` is, and that has the side-effect of changing the value of `add`. – Traveller Aug 07 '22 at 02:25
1

wow thanks i tested it with alert(add) and ur right! i did not know if statements worked like that thanks – Yagami_Light Aug 07 '22 at 02:33

why wont my else if statement work? (the if and else work, but not the if else statement even though condition is met)

1 Answers1