ideas

let firstNum = ""; // "2" or 2
let secondNum = ""; // "3" or 3
let operator = ""; // "+"
let result = "";

let mainDisplay = document.getElementById("display2");

let btn2 = document.getElementById("2").addEventListener("click", numberPress);
let btn3 = document.getElementById("3").addEventListener("click", numberPress);

document.getElementById("=").addEventListener("click", equalsPress);

document.getElementById("+").addEventListener("click", operatorPress);

// TEST CASE: 2 + 3 = 5

// STEP 1: Press 2
// EXPECT: 2 displays on the screen
// ACTUAL: IT WORKS!

// STEP 2: Press +
// EXPECT: 2 displays on the screen
// ACTUAL: IT WORKS!

// STEP 3: Press 3
// EXPECT: 3 displays on the screen
// ACTUAL: 22 displays on the screen

// STEP 4: Press =
// EXPECT: 5 display on the screen
// ACTUAL: 222 displays on the screen

function numberPress(e) {
    operator
    console.log("number button was pressed");
}

function operatorPress(e) {
    console.log("operator button was pressed");
}

function equalsPress(e) {
    console.log("equals button was pressed");
    console.log("firstNum: ", firstNum);
    console.log("secondNum: ", secondNum);
    console.log("operator: ", operator);
}