JavaScript 数组分片切割方法

问题

期望实现下面的效果 [1, 2, 3, 4, 5, 6, 7] -> [[1, 2, 3], [4, 5, 6], [7]]

实现

lodash

_.chunk(['a', 'b', 'c', 'd'], 2);
// => [['a', 'b'], ['c', 'd']]

_.chunk(['a', 'b', 'c', 'd'], 3);
// => [['a', 'b', 'c'], ['d']]

简单实现

var i,
  j,
  temporary,
  chunk = 10;
for (i = 0, j = array.length; i < j; i += chunk) {
  temporary = array.slice(i, i + chunk);
  // do whatever
}

reduce

var perChunk = 2; // items per chunk

var inputArray = ['a', 'b', 'c', 'd', 'e'];

var result = inputArray.reduce((resultArray, item, index) => {
  const chunkIndex = Math.floor(index / perChunk);

  if (!resultArray[chunkIndex]) {
    resultArray[chunkIndex] = []; // start a new chunk
  }

  resultArray[chunkIndex].push(item);

  return resultArray;
}, []);

console.log(result); // result: [['a','b'], ['c','d'], ['e']]

修改原型

Object.defineProperty(Array.prototype, 'chunk_inefficient', {
  value: function (chunkSize) {
    var array = this;
    return [].concat.apply(
      [],
      array.map(function (elem, i) {
        return i % chunkSize ? [] : [array.slice(i, i + chunkSize)];
      })
    );
  },
});

console.log([1, 2, 3, 4, 5, 6, 7].chunk_inefficient(3));
// [[1, 2, 3], [4, 5, 6], [7]]

slice

function chunk(array, size) {
  // This prevents infinite loops
  if (size < 1) throw new Error('Size must be positive');

  const result = [];
  for (let i = 0; i < array.length; i += size) {
    result.push(array.slice(i, i + size));
  }
  return result;
}