undy

undy is a small Javascript library to enable better handling for undefined values in deeply nested objects, similar to the null-conditional operator in other languages such as C#. This lets you write what you mean, and deal with undefined values only at the end instead of constantly checking for undefined values at every level of your object.

undy two functions: one that wraps your variable with undy(variable) to change their nested undefined behaviour, and the other to configure the property to get your value out, with undy.configure(newValue). All values retrieved from the new object are similarly wrapped. Call .value, or whatever you set in undy.configure(newValue) to retrieve your raw object back at any point in the chain.

Get Started

To install run npm install undy.

Include it in your project and use it as follows:

import undy, {configure} from 'undy'

var a = {b: {c: {d: 'e'}}}

// Returns either the value or undefined if somewhere in the chain an object doesn't exist
let val = undy(a).b.c.d.value // 'e'
val = undy(a).value // {b: {c: {d: 'e'}}}
val = undy(a).b.x.y.z.value // undefined
val = undy(a).b.value // {c: {d: 'e'}}

// Mutating an object wrapped by undy updates the underlying object
var wrapped = undy(a)
wrapped.b.c.d = 'hello'
console.log(a.b.c.d) // 'hello'

// Primitives return undefined for all property access except directly calling .value
var primitive = undy('hello')
val = primitive.a.value // undefined
val = primitive.a.b.c.value // undefined
val = primitive.value // 'hello'

// Change .value to anything you want by calling configure
const unWrap = Symbol.for('undy')
configure(unWrap)
val = undy(a).b.c.d[unWrap] // 'e'
val = undy(a).z[unWrap] // undefined

Compatability

undy works in all evergreen browsers, and in the latest version of Node.js. However since undy relies on ES2015 proxies, it does not work in IE 11 and below.