apps.js

'use strict'

const keys = document.querySelector('.calculator-keys');


const calculator = {
  displayValue: '0',
  firstOperand: null,
  waitingForSecondOperand: false,
  operator: null,
}
function inputDigit(digit){

  const {displayValue, waitingForSecondOperand} = calculator;
  if(waitingForSecondOperand === true){
    calculator.displayValue = digit;
    calculator.waitingForSecondOperand = false;
  }else{
  calculator.displayValue = displayValue === '0'? digit : displayValue + digit;
  }
}
function inputDecimal(dot){
 
  if(!calculator.displayValue.includes(dot)){
    calculator.displayValue += dot;
  }
}
function resetCalculator(){
  calculator.displayValue = '0';
  calculator.firstOperand = null;
  calculator.waitingForSecondOperand = false;
  calculator.operator = null;

}
function handleOperator(nextOperator){
  const{firstOperand, displayValue, operator} = calculator;
  const inputValue = parseFloat(displayValue);
  if(operator && calculator.waitingForSecondOperand){
    calculator.operator = nextOperator;
    return;
  }
  if(firstOperand === null){
    calculator.firstOperand = inputValue;
  }else if(operator){
    const currentValue = firstOperand || 0;
    const result = performCalculation[operator](firstOperand, inputValue);
    calculator.displayValue = String(result);
    calculator.firstOperand = result;
  }
  calculator.waitingForSecondOperand = true;
  calculator.operator = nextOperator;

}
const performCalculation = {
  '/': (firstOperand, secondOperand) => firstOperand/secondOperand,
  '*': (firstOperand, secondOperand) => firstOperand*secondOperand,
  '+': (firstOperand, secondOperand) => firstOperand+secondOperand,
  '-': (firstOperand, secondOperand) => firstOperand-secondOperand,
  '=': (firstOperand, secondOperand) => secondOperand

}
function updateDisplay(){
  const display = document.querySelector('.calculator-screen');
  display.value = calculator.displayValue;
}
updateDisplay();
keys.addEventListener('click', (event) => {
  const target = event.target;
  if(!target.matches('button')){
    return
  }
  if(target.classList.contains('operator')){
    handleOperator(target.value);
    updateDisplay()
    return
  }
  if(target.classList.contains('decimal')){
    inputDecimal(target.value);
    updateDisplay()
    return
  }
  if(target.classList.contains('all-clear')){
    resetCalculator();
    updateDisplay();
    return
  }
 inputDigit(target.value)
 updateDisplay()
});