将一维数组切分成二维数组：按照第二个参数（数字）的值，来决定二维数组长度

let arr1 = ['a','b','c','d','e','f','g'];

const chunk =(arr,chunkLength)=>{

const newArr = [];

const len = arr.length;

newArr[0] = arr.slice(0,chunkLength);

for(let i = chunkLength;i

if(newArr[newArr.length-1].length === chunkLength){

newArr.push([]);

// console.log(newArr);

}

newArr[newArr.length-1].push(arr[i]);

}

console.log(newArr);

}

let result = chunk(arr1,3);