1. // Underscore/Lodash
    2. console.log(grouped)
    3. // output: {1: [1.3], 2: [2.1, 2.4]}
    4. // Native
    5. var grouped = [1.3, 2.1, 2.4].reduce((r, v, i, a, k = Math.floor(v)) => ((r[k] || (r[k] = [])).push(v), r), {})
    6. // output: {1: [1.3], 2: [2.1, 2.4]}

    Browser Support for Array.prototype.reduce()