DOM Shopping

Multiply Quantity by Price

• You can change quantity
• Multiply the number by the price to get total cost

{expr:[{id:'total',prop:"value"}],
 actions:[{id:'recalculate',method:"click"},{id:'quantity',value:"2"},{id:'recalculate',method:"click"},]}

document.body.innerHTML = `
<div>Price: <input id=price disabled value='50'></div>
<div>Quantity: <input id=quantity value='1'></div>
<div><button id=recalculate>Recalculate</button></div>
<div>Total: <input id=total value='50' disabled></div>
`;

document.body.innerHTML = `
<div>Price: <input id=price disabled value='50'></div>
<div>Quantity: <input id=quantity value='1'></div>
<div><button id=recalculate>Recalculate</button></div>
<div>Total: <input id=total value='50' disabled></div>
`;
document.getElementById('recalculate').onclick = ()=>{
  document.getElementById('total').value =
    parseInt(document.getElementById('price').value) *
    parseInt(document.getElementById('quantity').value);
}

Sum Quantity by Price

• Adult ticket costs £10
• Child tickets costs £5

{expr:[{id:'total',prop:"value"}],
 actions:[{id:'adult',method:"onchange"},
          {id:'adult',value:"2"},
          {id:'adult',method:"onchange"},]}

document.body.innerHTML = `
<div>Adult: Quantity: <select id=adult value=1>
               <option>1</option>
               <option>2</option>
               </select>
</div>
<div>Child: Quantity: <select id=child value=1>
               <option>1</option>
               <option>2</option>
               </select>
</div>
<div>Total: <input id=total value='15' disabled></div>
`;
document.querySelectorAll('select').forEach(()=>{
})

document.body.innerHTML = `
<div>Adult: Quantity: <select id=adult value='1'>
               <option>1</option>
               <option>2</option>
               </select>
</div>
<div>Child: Quantity: <select id=child value='1'>
               <option>1</option>
               <option>2</option>
               </select>
</div>
<div>Total: <input id=total value='15' disabled></div>
`;
document.querySelectorAll('select').forEach(s=>{
  s.onchange = ()=>{
    document.getElementById('total').value =
      parseInt(document.getElementById('adult').value) * 10 +
      parseInt(document.getElementById('child').value) * 5;
  };
})