Pfthb

is there a way to reference an object's key as a variable and then change its value? I'm trying this

const obj = 
 x: 
 y: 
 z: 'test'
 
 


const func = () => 
 let root = obj['x'];
 root = 'test 2';


func();

console.log(obj);

I'm trying to figure this out as I'm writing a recursive function in order to change root to something more like obj['x']['y']

If I understand your question correctly, the answer is probably "not without doing really weird stuff." What I believe you are asking is this. Given:

const obj = 
 x: 
 y: 
 z: 'test'
 
 

you want to store obj.x (equivalently, obj['x']) into a variable, in such a way that assigning to that variable will actually mutate the x field of object obj. Now you cannot do that. Once you make the binding:

let root = obj.x

Then reassigning root will NOT change obj at all: root is a distinct variable from obj. Draw a picture, it will help. However, root is essentially a pointer to obj.x so if you did:

root.y = 'test 2'

than this does mutate obj.x.y.

But, note you cannot assign obj.x to a variable and then use that variable to mutate the x field of obj. You can only mutate fields WITHIN obj.x. JavaScript does not have the ability to alias things (or make lvalues) like C++, for instance.

If you really want to update the x property of obj then you should put ONLY the string x into a variable like this:

root = 'x'

then you can do:

obj[root] = 'a new value for obj.x'

and this will mutate obj.x. But remember, you cannot first evaluate obj.x and then use that result to mutate obj.x. Well, I mean, not without doing some really nasty stuff like this:

root = 'obj.x';
eval(`$root = 'a new value for obj.x';`);

But don't.

By the way, if obj was also a variable, then you could do this:

receiver = obj;
prop = 'x';
Reflect.set(receiver, prop, 'the new value')

Hopefully I guessed what you were trying to do. At any rate, maybe this answer will give some ideas.

const func = () => 
 let root = obj['x'];
 root = 'test 2';

This reassigns the variable root to a new value and does not affect the object. Instead, assign to the object directly:

obj['x'] = 'test 2'

const obj = 
 x: 
 y: 
 z: 'test'
 
 


const func = () => 
 obj['x'] = 'test 2';


func();

console.log(obj);

Or you can change the value at a key via the root variable:

const obj = 
 x: 
 y: 
 z: 'test'
 
 


const func = () => 
 let root = obj['x'];
 root['y'] = 'test 3';


func();

console.log(obj);

Just pass the values

const obj = x:
y:
z: 'test'

delete Object.assign(obj, newKey: obj.oldKey ).oldKey;