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;
const key = 'x'; obj[key] = 'test 2';