如何快速實現(xiàn)數(shù)組的轉(zhuǎn)換？

let b = a.reduce((r,c,i)=>{
  let index = parseInt(i/2);
  if(r[index] === undefined) r[index] = [];
  r[index].push(c);
  return r;
}, []).map(o=>o.length>1?o:o[0]);

console.log(b);

如果上面能看懂，再給一個簡化版的

a.reduce((r,c,i,a)=>{
  if(i%2 === 1) r.push([a[i-1], c]);
  if(i%2 === 0 && i === a.length - 1) r.push(c);
  return r;
}, [])

function piecewise(ary, size) {
    var ary = ary.slice()
        len = ary.length,
        retAry = []

    if ( len < size ) {
        return [ary];
    }


    var count = Math.floor(len / size) + (len % size == 0 ? 0 : 1)

    while(count--) {
        retAry.push(ary.splice(0, size))
    }

    return retAry
}

var ary = [1,2,3,4,5]
piecewise(ary, 2) 

希望對你有幫助

a.reduce((arr, item, index) => {
    index%2===0 && arr.push([item]);
    index%2===1 && arr[arr.length-1].push(item);
    return arr;
}, [])