Is there a short-hand to do the following:
let o = {}
o['a'] = 1;
o['b'] = 2;
For example, either:
let o = {}
o.update({'a': 1, 'b': 2})
Or:
let o = {'a': 1, 'b': 2}
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1 Answer
Object.assign can achieve it.
const o = { original: 'orig' };
Object.assign(o, {'a': 1, 'b': 2});
console.log(o);
answered Oct 8, 2021 at 21:25
CertainPerformance
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6 Comments
David542
thanks, why do you declare it as
const in the above case? Wouldn't the updating of the object make it 'un-const' ?
CertainPerformance
const indicates that the variable won't be reassigned - that o = somethingElse won't happen later. It's good practice to use const to declare variables when possible (which it is, 95% of the time) to make code more readable. Reassignment is not the same thing as mutation. Mutation assigns to a property of the object, reassignment changes what the whole variable name points to. const only prohibits reassignment.David542
thanks, that's a really helpful explanation. By the way, to look up all the properties/methods of an object, how do you normally do that? For example in python I'll do something like:
dir(set()) and get ['pop', 'remove', ...].CertainPerformance
Object.keys usually. If you want the values too, Object.entries. Only values: Object.values. Non-enumerable properties too (rare): Object.getOwnPropertyNames. Properties that are non-enumerable and prototypal: recursive Object.getOwnPropertyNamesDavid542
Do you have to enumerate them in a
for loop in order to read them? For example, if I just do: console.log(Object.keys, Object.values, Object.values); it prints [Function: keys] [Function: values] [Function: values]. |