how to build a calculator in javascript code example

Example 1: a simple javascript calculator

<div class="calculator">

  <input type="text" class="calculator-screen" value="" disabled />
  
  <div class="calculator-keys">
    
    <button type="button" class="operator" value="+">+</button>
    <button type="button" class="operator" value="-">-</button>
    <button type="button" class="operator" value="*">×</button>
    <button type="button" class="operator" value="/">÷</button>

    <button type="button" value="7">7</button>
    <button type="button" value="8">8</button>
    <button type="button" value="9">9</button>


    <button type="button" value="4">4</button>
    <button type="button" value="5">5</button>
    <button type="button" value="6">6</button>


    <button type="button" value="1">1</button>
    <button type="button" value="2">2</button>
    <button type="button" value="3">3</button>


    <button type="button" value="0">0</button>
    <button type="button" class="decimal" value=".">.</button>
    <button type="button" class="all-clear" value="all-clear">AC</button>

    <button type="button" class="equal-sign operator" value="=">=</button>

  </div>
</div>

Example 2: how to make a calculator websiteJS

let add =(...params) => {
    let sum = 0;
    params.forEach(el =>{
        sum = sum + parseInt(el);
    })
    return sum
}

document.querySelector('.add').addEventListener('click' , function (e) {
    const adder = document.querySelector('.addinput').value 
    const meow = adder.split(',')
    let result = add(...meow)
    if (isNaN(result)) {
        result = 'ENTER A NUMBER'
    }
    document.querySelector('.result').textContent = result
})

let times =(...params) => {
    let multiply = 1;
    params.forEach(el =>{
        multiply = multiply * el;
    })
    return multiply
}

document.querySelector('.multiply').addEventListener('click' , function (e) {
    const multiplier = document.querySelector('.multiplyinput').value 
    const moo = multiplier.split(',')
    let product = times(...moo)
    if (isNaN(product)) {
        product = 'ENTER A NUMBER'
    }
    document.querySelector('.product').textContent = product
})

let subtract =(...params) => {
    let diff = 0;
   diff = params[0] - params[1]
    return diff
}

document.querySelector('.subtract').addEventListener('click' , function (e) {
    const subtracter = document.querySelector('.subtractinput').value 
    const woof = subtracter.split(',')
    let diff = subtract(...woof)
    if (isNaN(diff)) {
        diff = 'ENTER A NUMBER'
    }
    document.querySelector('.difference').textContent = diff
})

let divide =(...params) => {
    let quotient = 0;
    quotient = params[0] / params[1]
    return quotient
}

document.querySelector('.divide').addEventListener('click' , function (e) {
    const divider = document.querySelector('.divideinput').value 
    const moo2 = divider.split(',')
    let quotient = divide(...moo2)
    if (isNaN(quotient)) {
        quotient = 'ENTER A NUMBER'
    }
    document.querySelector('.quotient').textContent = quotient
})