array_reducer_example_03.js

const survey = [
	{ name: "Zuri", votedFramework: 'react' },
	{ name: "Sofia", votedFramework: 'angular' },
	{ name: "Elon", votedFramework: 'react' },
	{ name: "Joe", votedFramework: 'react' },
	{ name: "Alex", votedFramework: 'angular' },
	{ name: "Josh", votedFramework: 'vue' },
	{ name: "Jade", votedFramework: 'react' },
	{ name: "Ted", votedFramework: 'angular' },
	{ name: "Leo", votedFramework: 'react' },
	{ name: "Nala", votedFramework: 'react' },
	{ name: "Jack", votedFramework: 'react' },
	{ name: "Fiadh", votedFramework: 'vue' },
];

const reducerCallback = (prevItem, vote) => { 
	if (prevItem[vote.votedFramework] === undefined) {
		return { ...prevItem, [vote.votedFramework]: 1 }
	}

	return { ...prevItem, [vote.votedFramework]: prevItem[vote.votedFramework] + 1 }
}

console.log(survey.reduce(reducerCallback, {})) // { "react": 7, "angular": 3, "vue": 2 }