使用嵌套对象和默认值进行解构

Question

I'm using destructuring to declare some variables like this:

const { a, b, c } = require('./something'),
    { e = 'default', f = 'default'} = c;

Is there a way to make this into single line? I've tried something like :

const { a, b, c = { e = 'default', f = 'default'} } = require('./something');

But it gives me an error:

SyntaxError: Invalid shorthand property initializer

Answer 1

The above code will not work if the object does not have c in it

 const { a, b, c: { e = 'default', f = 'default'}} = {a: 1, b: 2} console.log(`a: ${a}, b: ${b}, e: ${e}, f: ${f}`)

This will print out an error. For completion, you could as a simple "={}" as default

 const { a, b, c: { e = 'default', f = 'default'} ={} } = {a: 1, b: 2} console.log(`a: ${a}, b: ${b}, e: ${e}, f: ${f}`)

Answer 2

Just replace = with : :

const {a, b, c: {e = 'default', f = 'default'}} = require('./something')

Demo:

 const { a, b, c: { e = 'default', f = 'default'} } = {a: 1, b: 2, c: {e: 3}} console.log(`a: ${a}, b: ${b}, e: ${e}, f: ${f}`)

It prints:

a: 1, b: 2, e: 3, f: default

Answer 3

This example will help you to understand the destructing of array and object with fallback values.

You can use the = symbol for adding fallback or default value while destructing.

 const person = { firstName: 'Nikhil', address: { city: 'Dhule', state: 'MH' }, /*children: [ { name: 'Ninu', age: 3 } ]*/ } const { firstName, address: { city, state }, children: { 0: { name='Oshin' // Fallback for name is string ie 'Oshin' }={} // Fallback for 1st index value of array is blank object }=[] // Fallback for children is blank array } = person; console.log(`${firstName} is from ${city} and his first child name is ${name}`);