在多种条件下进行短路评估的最简洁方法

Question

I am trying to build a JSON object based on data that the client has on hand.

Ideally, it would select address data if available, then cart data if not available, otherwise null.

Here the data is retrieved from localStorage, but I run into issues, addresses and cart resolve the following errors when null .

Cannot read property 'length' of null

Cannot read property 'idShipTo' of undefined

let cart = JSON.parse(localStorage.getItem('shopping-cart'));
let addresses = JSON.parse(localStorage.getItem('customer-address'));

this.request = {
  address: {
    shipToAddLine: addresses[0].shipToAddLine || cart.shipToAddLine || null,
    shipToCityStZip: addresses[0].shipToCityStZip || cart.shipToCityStZip || null
  }
}

I'd like to use something like the ternary operator, but use more than one if / else value.

this.request = {
  address: {
    shipToAddLine: (addresses) ? addresses[0].shipToAddLine || (cart) ? cart.shipToAddLine || null,
    shipToCityStZip: (addresses) ? addresses[0].shipToCityStZip || (cart) ? cart.shipToCityStZip || null
  }
}

Is this possible using a clean (one-line) syntax in JS, or do I have to put the assignments in if / else blocks?

let shipToAddLine;
if (addresses) shipToAddLine = addresses[0].shipToAddLine;
else if (cart) shipToAddLine = cart.shipToCityStZip;
else shipToAddLine = null;

etc...

Answer 1

您可以链接三元运算符

    shipToAddLine: addresses ? addresses[0].shipToAddLine : (cart ? cart.shipToAddLine : null),

Answer 2

You can use initialize it to appropriate empty values if not present

let cart = JSON.parse(localStorage.getItem('shopping-cart')) || {};
let addresses = JSON.parse(localStorage.getItem('customer-address')) || [{}];

this.request = {
  address: {
    shipToAddLine: addresses[0].shipToAddLine || cart.shipToAddLine || null,
    shipToCityStZip: addresses[0].shipToCityStZip || cart.shipToCityStZip || null
  }
}

If cart is null, it is initialized to an empty object and if address is null initially it is initialized to an array having an empty object. Then you will not need checks before addresses[0].shipToAddLine and cart.shipToAddLine