Suppose I have an object (baz) of variable contents. How can I assign a sub-object (foo) with a key (baz) to that object in one line?

Examples:

var baz = {}
baz.foo.bar = 1;
console.assert(baz === { foo: { bar: 1 } });

(or, in the case where foo is already defined)

var baz = { foo: { 1: "b" } };
baz.foo.bar = 1;
console.assert(baz === { foo: { 1: "b", bar: 2 } });

CodePudding user response：

It's possible to put all in one line, though personally I wouldn't recommend it. You're technically doing two pretty different things:

• Assign an object as a property if the object doesn't exist yet
• Assign a property if the object already exists, mutating the existing object

You can assign baz.foo or the empty object to baz.foo, then assign the bar property value to the resulting object:

const baz = {};
(baz.foo ??= {}).bar = 1;
console.log(baz.foo.bar);

const baz2 = {};
(baz2.foo ??= {}).bar = 1;
console.log(baz2.foo.bar);

I'd prefer

// Create the object if it doesn't exist yet
baz.foo ??= {};
// Assign the new nested value
baz.foo.bar = 1;

Code readability is more important than golfing in most cases.

CodePudding user response：

For the first case :

baz.foo = {bar :1}

And your code works for the second case

(Note that the following code outputs false :

a = {b:1}
console.log(a==={b:1})

)