Set key dynamically inside map() in javascript?

Question

So I know how to set the key dynamically like this:

var hashObj = {};
hashObj[someValue] = otherValue;

But I haven't seen any answer regarding map():

var list = ['a', 'b', 'c'];

var hashObject = list.map(function(someValue) {
    return { someValue: 'blah' };
});

// should return: [ {'a': 'blah'}, {'b': 'blah'}, {'c': 'blah'} ];

I know I can do this in a for loop and such, but is this not possible in javascript using just map()?

Answer 1

You need to get someValue to be evaluated as its value. If you use object notation, it will be interpreted literally as string.

You can use a temporary object to achieve what you want:

var list = ['a', 'b', 'c'];

var hashObject = list.map(function(someValue) {
    var tmp = {};
    tmp[someValue] = 'blah';
    return tmp;
});

Answer 2

I know it is really old question, but answer can be helpful for others.

As it has been already said, Array.prototype.map is used to get new array.

But if you want to get object instead of array - maybe you should think about using Array.prototype.reduce (https://developer.mozilla.org/pl/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce)?

const list = ['a', 'b', 'c'];

const hashObject = list.reduce((acc, current) => {
  acc[current] = 'blah';
  return acc;
}, {});

// hashObject equals: {"a":"blah","b":"blah","c":"blah"}

And if you want achieve the same result as mentioned in your question, you can use Array.prototype.map of course:

const list = ['a', 'b', 'c'];

const hashArrayOfObjects = list.map((current) => {
  return {[current]: 'blah'};
});

// hashArrayOfObjects equals: [{"a":"blah"},{"b":"blah"},{"c":"blah"}]

You can check how it works on CodePen: https://codepen.io/grygork/pen/PojNrXO