yiningv

📊 每周工作报告

yiningv

function frequencies_by(enumerable, key_fn) {
    key_fn = key_fn || (x => x);
    const result = {};
    enumerable.forEach(e => {
        const key = key_fn(e);
        result[key] = result[key] || 0;
        result[key] += 1;
    });
    return result;
}