Merge multiple objects

[rajlomror]

Merge multiple objects into an object.

[elkarouani]

Hi @rajlomror, the solution that you did is for two objects not for multiple objects

[WiXSL]

Suggested change

	const mergeObjects = (obj1, obj2) => Object.assign(obj1, obj2);
	const mergeObjects = (...objs) => Object.assign({}, ...objs);

[elkarouani]

Good solution, but better not using too much spreading as it can kill performance.
Both our solutions can be added in that markdown file.

[WiXSL]

Sure, is just a suggestion, please, add the best possible solution

[elkarouani]

I can consider this solution instead :

const mergeObjects = (...objects) => objects.reduce((lookup, obj) => { Object.keys(obj).forEach(key => { lookup[key] = obj[key]; }); return lookup; }, {});

console.log(mergeObjects({a: 2, b: 4}, {c: 1}));    // { a: 2, b: 4, c: 1 }

[robinpokorny]

Hey, @rajlomror, that is a great use of JavaScript! However, I'm not sure if using a build-in construct should be considered a utility function. Why not use it directly? What is there extra?

@elkarouani, the function you wrote works well and while it cannot be optimized by the VM (like native ones) it's actually quite OK-performant. One thing to keep in mind is that this ignores all symbol properties which object spread would keep.

[elkarouani]

Hey, @rajlomror, that is a great use of JavaScript! However, I'm not sure if using a build-in construct should be considered a utility function. Why not use it directly? What is there extra?

I think this utility can be helpful in some cases where you want to manipulate or organize objects.

@elkarouani, the function you wrote works well and while it cannot be optimized by the VM (like native ones) it's actually quite OK-performant. One thing to keep in mind is that this ignores all symbol properties which object spread would keep.

Thank you @robinpokorny for reviewing my solution, do you have an example for that point of ignoring symbol properties so I can understand it more ?

[robinpokorny]

@elkarouani, sure, look at this code:

const o = {
  a: 1,
  [Symbol.toPrimitive]: () => 2,
};

const p = {
  a: 3,
};

const r = { ...o, ...p };

const mergeObjects = (...objects) => objects.reduce((lookup, obj) => { Object.keys(obj).forEach(key => { lookup[key] = obj[key]; }); return lookup; }, {});
const s = mergeObjects(o, p)

console.log(1 + r)
// -> 2

console.log(1+s)
// -> '1[object Object]'