JavaScript Calculator Help: Subtraction Not Working

JavaScript
1

I’m working on the Calculator project, but I’m running into an issue where subtraction isn’t working in some cases. For something simple, like 5 -2, I get the expected result. For something a little bit more complicated, like the case the test runner uses, it fails (in that instance, returning 33 - 0.5 instead of 32.5). Here’s the relevant code:

calculateTotal = () => {
    const displayElements = this.state.display.split(' ');

    // Checking for multiple consecutive operators isn't working
    // yet, but it's not what I'm concerned about here
    displayElements.forEach((element, index) => {
      if (
        this.operators.includes(element) &&
        this.operators.slice(0, 4).includes(displayElements[index + 1])
      ) {
        displayElements.splice(index, 1);
      }
    })

    displayElements.forEach((element, index) => {
      if (element === '*' || element === '/') {
        const firstNumber = displayElements[index - 1];
        const secondNumber = displayElements[index + 1];
        if (element === '*') {
          let result = firstNumber * secondNumber;
          displayElements.splice(index - 1, 3, result);
        }

        if (element === '/') {
          let result = firstNumber / secondNumber;
          displayElements.splice(index - 1, 3, result);
        }
      }
    });

    displayElements.forEach((element, index) => {
      if (element === '+' || element === '-') {
        const firstNumber = displayElements[index - 1];
        const secondNumber = displayElements[index + 1];
        if (element === '+') {
          let result = +firstNumber + +secondNumber;
           console.log(result);
          displayElements.splice(index - 1, 3, result);
        }

        if (element === '-') {
          let result = firstNumber - secondNumber;
          displayElements.splice(index - 1, 3, result);
        }
      }
    });

    this.setState({ display: displayElements });
  };

Multiplication, Division, and Addition all work as expected, and return the expected value if I log the result var after the operation, but it never logs it with subtraction, even in the simpler cases that work that I mentioned earlier. I’ve tried wrapping the values in Number, parseFloat, etc all to no avail. If someone can point out what I’m overlooking here, I’d appreciate it!

2

check this line first

3

The plus signs in that expresssion typecast the strings into numbers, it’s not the issue.

4

I noticed my error after stepping away from this project for a bit: the loops only ran once each, causing them to be incomplete. Working code looked something like this:

  while (displayElements.includes('+') || displayElements.includes('-')) {
      displayElements.forEach((element, index) => {
        const firstNumber = displayElements[index - 1];
        const secondNumber = displayElements[index + 1];

        if (element === '+') {
          let result = +firstNumber + +secondNumber;
          displayElements.splice(index - 1, 3, result);
          console.log(displayElements);
        }

        if (element === '-') {
          let result = firstNumber - secondNumber;
          displayElements.splice(index - 1, 3, result);
          console.log(displayElements);
        }
      });
    }