JavaScript：使用.forEach 将新属性添加到数组项

Question

let foods = [
  { name: 'bread', carbs: 36, protein: 8, fat: 2 },
  { name: 'mayo mustard mix', carbs: 0, protein: 0, fat: 10 },
  { name: 'turkey', carbs: 0, protein: 25, fat: 1 },
  { name: 'cheese', carbs: 0, protein: 5, fat: 7 },
]

I need to calculate the calories by multiplying carbs, protein, and fat together and then add the results together.

Im pretty stuck on this one, i've gotten to

foods.forEach((element, index, array => { })

but not really sure where to go from there.

Answer 1

For each food item, get its three values and save the calculation, if I remember it correctly:), in a new property calories :

 let foods = [ { name: 'bread', carbs: 36, protein: 8, fat: 2 }, { name: 'mayo mustard mix', carbs: 0, protein: 0, fat: 10 }, { name: 'turkey', carbs: 0, protein: 25, fat: 1 }, { name: 'cheese', carbs: 0, protein: 5, fat: 7 } ]; foods.forEach(food => { const { carbs = 0, protein = 0, fat = 0 } = food; food.calories = carbs * 4 + protein * 4 + fat * 9; }); console.log(foods);

Answer 2

function calculate_calories ( food ) { return something }
// this function should calculate the calories from input
// I assume you will do this one yourself

foods.forEach( food => {
  var cal = calculate_calories ( food )
  food.calories = cal
})

That's it. I hope it's understandable enough.