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In ES6, you use the Map object to reliably count objects of arbitrary types

Techvibes Dev answered on December 15, 2022 Popularity 1/10 Helpfulness 1/10

answer In ES6, you use the Map object to reliably count objects of arbitrary types

In ES6, you use the Map object to reliably count objects of arbitrary types

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class Counter extends Map {
    constructor(iter, key=null) {
        super();
        this.key = key || (x => x);
        for (let x of iter) {
            this.add(x);
        }
    }
    add(x) {
      x = this.key(x);
      this.set(x, (this.get(x) || 0) + 1);
    }
}

// again, with no classifier just count distinct elements

results = new Counter([1, 2, 3, 1, 2, 3, 1, 2, 2]);
for (let [number, times] of results.entries())
    console.log('%s occurs %s times', number, times);


// counting objects

people = [
    {name: 'Mary', gender: 'girl'},
    {name: 'John', gender: 'boy'},
    {name: 'Lisa', gender: 'girl'},
    {name: 'Bill', gender: 'boy'},
    {name: 'Maklatura', gender: 'girl'}
];


chessChampions = {
    2010: people[0],
    2012: people[0],
    2013: people[2],
    2014: people[0],
    2015: people[2],
};

results = new Counter(Object.values(chessChampions));
for (let [person, times] of results.entries())
    console.log('%s won %s times', person.name, times);

// you can also provide a classifier as in the above

byGender = new Counter(people, x => x.gender);
for (let g of ['boy', 'girl'])
   console.log("there are %s %ss", byGender.get(g), g);
 Run code snippet

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Source: stackoverflow.com

Tags: count map object types whatever

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Contributed on Dec 15 2022

Techvibes Dev

0 Answers Avg Quality 2/10

In ES6, you use the Map object to reliably count objects of arbitrary types

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