add array of keys as property on obj as accumulator by reduce?

Question

i have array of keys that i want to add as property with calculated val(not including on code) on empty object like this by reduce:

const f = ['a','b','c'].reduce((obj,key) => obj[key]='', {})

i was expecting the obj is the accumulator {} so i added properties that way? how do i make this work by reduce?

i was expecting and want it to result like this for that code:

{ a:'',  b:'', c:'' }

but my code only results to empty string on console. how do i achieve it?

Answer 1

The value that the reduce callback returns will be the accumulator in the next iteration. So, in your code, obj only refers to the object in the first iteration - on the next iteration, it refers to what obj[key] = '' resolves to, which is the empty string.

Return the object instead:

 const f = ['a', 'b', 'c'].reduce((obj, key) => { obj[key] = ''; return obj; }, {}); console.log(f); 

You could use Object.fromEntries instead, if you wanted (though, it's very new, so for good cross-browser support, include a polyfill):

 const f = Object.fromEntries( ['a', 'b', 'c'].map(key => [key, '']) ); console.log(f);