題目：產生10個隨機數[1,2,3,4, 10, 11, 4, 20],結果[[1,2,3,4], [10,11],[20]]

// start 開始值  end 結束值 （區間） length 隨機個數
Array.prototype.random = (start, end, length) => {
	let i = 0
	const results = []
	while(i < length) {
		const random = ~~(Math.random() * end) + 1
		random > start && (() => {
            results.push(random)
            i ++
        })()
	}
	return results
}
const arr = [].random(1, 20, 100).reduce((frant, cur) => {
    const i = ~~(cur / 10)
    frant[i] = [ ...( frant[i] || [] ), ...[cur] ]
    return frant
}, [])

console.log(arr)