Is there a Javascript function similar to the Python Counter function?

Question

I am attempting to change a program of mine from Python to Javascript and I was wondering if there was a JS function like the Counter function from the collections module in Pyt

Answer 1

I know I'm late but in case if someone is looking at this in 2020 you can do it using reduce, for example:

const counter = (list) => {
  return list.reduce(
    (prev, curr) => ({
      ...prev,
      [curr]: 1 + (prev[curr] || 0),
    }),
    {}
  );
};

console.log(counter([1, 2, 1, 1, 1, 1, 2, 3, 4, 5, 6, 7, 1, 0]));
// output -> { '0': 1, '1': 6, '2': 2, '3': 1, '4': 1, '5': 1, '6': 1, '7': 1 }

more advance example with a callback function and context binding

const data = [1, 2, 3, 4, 5];

const counter = (list, fun, context) => {
  fun = context ? fun.bind(context) : fun;
  return list.reduce((prev, curr) => {
    const key = fun(curr);
    return {
      ...prev,
      [key]: 1 + (prev[key] || 0),
    };
  }, {});
};


console.log(counter(data, (num) => (num % 2 == 0 ? 'even' : 'odd')));
// output -> { odd: 3, even: 2 }