把一个数组分割成多个数组

function group(array, num) {
    let index = 0
    const newArray = []
    while (index < array.length) {
      newArray.push(array.slice(index, (index += num)))
    }
    return newArray
  }

group(数组数据，每组数据长度)

const a=[1,2,3,4,5,6,7,8,9]
const b= group(a,5)
	  b=[
			[1,2,3,4,5],
			[6,7,8,9]
		]