I would like to have this object:
const m = {a:undefined, b:undefined, d:undefined};
but would prefer to produce it from an array:
const m = {}
const l = ["a","b","c"];
for (const i in l){
m[l[i]] = undefined;
}
But what would be a nicer way of doing this when using es6?
You could use for/of, but Array#reduce (which exists since ES5) might be more elegant:
const m = ['a', 'b', 'c'].reduce((o, k) => (o[k] = undefined, o), {});
However, if you need this a lot, I'd recommend to create a reusable function with a proper name.
You can Array#map each property to an object, and combine them using the spread syntax, and Object#assign:
const m = Object.assign(...['a', 'b', 'c'].map((prop) => ({ [prop]: undefined })));
console.log(m);
