Meaning of variable in array as property name?

Question

var expertise = \'journalism\'
var person = {
    name: \'Sharon\',
    age: 27,
    [expertise]: {
        years: 5,
        interests: [\'international\', \'politics\'         


        

Answer 1

It is syntactic sugar, introduced in ECMAScript 6

Computed property names

Starting with ECMAScript 2015, the object initializer syntax also supports computed property names. That allows you to put an expression in brackets [], that will be computed as the property name. This is symmetrical to the bracket notation of the property accessor syntax, which you might have used to read and set properties already.

ECMAScript 5

var expertise = 'journalism'
var person = {
    name: 'Sharon',
    age: 27
}
person[expertise] = {
    years: 5,
    interests: ['international', 'politics', 'internet']
}

ECMAScript 6

var expertise = 'journalism'
var person = {
    name: 'Sharon',
    age: 27,
    [expertise]: {
        years: 5,
        interests: ['international', 'politics', 'internet']
    }
}