Exercise – a basic calculator

With our knowledge of Booleans, numbers, and strings, let's build a basic calculator. Begin by cloning the repository at https://github.com/PacktPublishing/Hands-on-JavaScript-for-Python-Developers/tree/master/chapter-4/calculator/starter-code.

You can safely ignore the HTML and CSS for the most part, but a readthrough of the HTML will help. Let's take a look at the JavaScript:

window.onload = (() => {
  const buttons = document.getElementsByTagName('button')
  const output = document.getElementsByTagName('input')[0]
  let operation = null
  let expression = firstNumber = secondNumber = 0

  output.value = expression

  const clickHandler = ((event) => {
    let value = event.target.value

    /** Write your calculator logic here.
        Use conditionals and math to modify the output variable.

        Example of how to use the operators object:
          operators['='](1, 2) // returns 3

        Expected things to use...