javascript - 从函数返回修改后的新对象

Question

从函数修改和返回新对象的最佳做法是什么？

我写了下面的函数:

export const addItemToCart = (currentCart, item) => {
  const { name, ...otherProps } = item;

  //if item exist in the cart
  if (currentCart[name]) {
    currentCart[name]["quantity"]++;
    return currentCart;
  } 
  //if the item does not exist
  else
  {
    currentCart[name] = { ...otherProps };
    currentCart[name]["quantity"] = 1;
    return currentCart;
  }

// the function must return a new modified object on each call
};

显然，硬编码属性“数量”和返回语句肯定可以改进。

如何改进此函数以使其更具可读性？

Answer 1

更多的“可读性”是非常基于意见的，无论哪种方式，你都可以尝试这样的事情:

const currentCart = {
  hello: {
    quantity: 1
  }
};

const addItemToCart = (currentCart, item) => {
  const { name } = item;

  // Short circuit + return the last value
  const quantityPrev = currentCart[name] && currentCart[name].quantity;

  // Or operator on boolean expression
  const quantity = 1 + (quantityPrev || 0);

  // Destructing for shallow copy, dynamic key assign
  return { ...currentCart, [name]: { quantity } };
};

console.log(addItemToCart(currentCart, { name: 'hello' }));
console.log(addItemToCart(currentCart, { name: 'blazer' }));