如何在Javascript中的每N个数组中添加项目

Question

在初始阶段，我有一个对象数组：

[
 { type: 'all' },
 { type: 'all' },
 { type: 'all' },
 { type: 'fruit'},
 { type: 'all' },
 { type: 'all' },
 { type: 'fruit' },
 { type: 'all' },
 { type: 'all' },
 { type: 'fruit' },
 { type: 'fruit' }
]

我想插入：

1）对象：{type：'toys'}每5个项目类型：全部

2）对象：{type：'clothes'}每2个项目类型：'fruit'

预期结果：

[
 { type: 'all' },
 { type: 'all' },
 { type: 'all' },
 { type: 'fruit'},
 { type: 'all' },
 { type: 'all' },
 { type: 'toys' },
 { type: 'fruit' },
 { type: 'clothes' },
 { type: 'all' },
 { type: 'all' },
 { type: 'fruit' },
 { type: 'fruit' },
 { type: 'clothes' }
]

我该如何实现这个功能？我试图forEach添加项目，但在推送项目后，array_demo长度发生了变化，难以测量哪个是列表的下一个原始项目。

array_demo.forEach((item, index) => {
  array_demo.push({type: 'demo'});
  console.warn(index);
});

Answer 1

你可以利用减少并保持所有和水果的数量

const array_demo = [
 { type: 'all' },
 { type: 'all' },
 { type: 'all' },
 { type: 'fruit'},
 { type: 'all' },
 { type: 'all' },
 { type: 'fruit' },
 { type: 'all' },
 { type: 'all' },
 { type: 'fruit' },
 { type: 'fruit' }
]

let all = 0;
let fruit = 0;
const newArray = array_demo.reduce((acc, item, index) => {
  if(item.type === 'all') {
     if(all === 4) {
       acc.push(item);
       acc.push({type: 'toys'})
       all = 0;
       return acc;
     } else {
       all++;
     }
  }else if(item.type === 'fruit') {
    if(fruit === 1) {
       acc.push(item);
       acc.push({type: 'clothes'})
       fruit = 0;
       return acc;
     } else {
       fruit++;
     }
    
  }
  acc.push(item);
  return acc;
  
}, []);
console.log(newArray);

Answer 2

一种简单而传统的方法：

let init = [
 { type: 'all' },
 { type: 'all' },
 { type: 'all' },
 { type: 'fruit'},
 { type: 'all' },
 { type: 'all' },
 { type: 'fruit' },
 { type: 'all' },
 { type: 'all' },
 { type: 'fruit' },
 { type: 'fruit' }
]

let last = [];
let allCounter = 0;
let fruitCounter = 0;

for (let type of init) {
	last.push(type);

	if (type.type == 'all' ) {
		allCounter++;
		if (allCounter == 5) {
			last.push({type:'toys'})
			allCounter = 0;
		}
	} else if (type.type == 'fruit') {
		fruitCounter++;
		if (fruitCounter == 2) {
			last.push({type: 'clothes'})
			fruitCounter = 0;
		}
	}
}

console.warn(last)

Answer 3

其他解决方案，结果相同

function insertion(my_array){
    var i=0,
        j=0,
        n=my_array.length,
        k=0;
    while(k<n){
        if(my_array[k].type=='all'){
            i++;console.log(i);
        }else if(my_array[k].type=='fruit'){
            j++;console.log(j);
        }
        if(i==5){
            k++;
            my_array.splice(k,0,{ type: 'toys' });
            i = 0;
            n++;
        }else if(j==2){
            k++;
            my_array.splice(k,0,{ type: 'clothes' });
            j = 0;
            n++;
        }
        k++;
    }
    return my_array;
}

Answer 4

var data = 
[
 { type: 'all' },
 { type: 'all' },
 { type: 'all' },
 { type: 'fruit'},
 { type: 'all' },
 { type: 'all' },
 { type: 'fruit' },
 { type: 'all' },
 { type: 'all' },
 { type: 'fruit' },
 { type: 'fruit' }
];

var result = [];
var allCounter = 0;
var fruitCounter = 0;
data.forEach(function(item,index){
  result.push(item);
  if(item.type == "all"){
    allCounter++;
  }
  if(item.type == "fruit"){
    fruitCounter++;
  }
  if(allCounter == 5){
    result.push({"type":"toys"});
    allCounter = 0;
  }
  if(fruitCounter == 2){
    result.push({"type":"clothes"})
    fruitCounter = 0;
  }
});

console.log(result);

Answer 5

您可以Array#map数据，并使用2个外部计数器（fruit和all）来计算每个计数器的出现次数。对于具有其中一种类型的每个对象，递增计数器，并检查它是否为第二个水果/ 5全部。如果它符合条件，则返回包含原始对象和添加对象的新数组。然后在spreading中用Array#concat压平所有子阵列。

注意：该解决方案使用@NinaScholz types object使其更通用。

const data = [{"type":"all"},{"type":"all"},{"type":"all"},{"type":"fruit"},{"type":"all"},{"type":"all"},{"type":"fruit"},{"type":"all"},{"type":"all"},{"type":"fruit"},{"type":"fruit"}];

const types = {
    all: { count: 0, size: 5, type: 'toys' },
    fruit: { count: 0, size: 2, type: 'clothes' }
};

const result = [].concat(...data.map((o) => {
  const to = types[o.type];

  return !to || ++to.count % to.size ? o : [o, { type: to.type }];
}));

console.log(result);

Answer 6

如果找到正确的外观数量并将新对象添加到数组中，您可以计算出现并插入。

为了计算和保持逻辑，这个appoach使用一个带有所需类型的对象作为键和所有其他值，如size和type用于插入。

{
    all: {
        count: 0,
        size: 5,
        type: 'toys'
    },
    fruit: {
        count: 0,
        size: 2,
        type: 'clothes'
    }
}

var array = [{ type: 'all' }, { type: 'all' }, { type: 'all' }, { type: 'fruit'}, { type: 'all' }, { type: 'all' }, { type: 'fruit' }, { type: 'all' }, { type: 'all' }, { type: 'fruit' }, { type: 'fruit' }],
    types = { all: { count: 0, size: 5, type: 'toys' }, fruit: { count: 0, size: 2, type: 'clothes' } },
    type,
    i = 0;

while (i < array.length) {
    type = types[array[i].type];
    if (type && ++type.count === type.size) {
        array.splice(++i, 0, { type: type.type });
        type.count = 0;
    }               
    ++i;
}

console.log(array);

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Answer 7

得到了类似的需求：

const concatAt = (array, predicate, value) => array.reduce(
    (c, n, idx) => {
        const at = typeof predicate === 'function' ? predicate(idx, n, array) : predicate === idx
        const newValue = typeof value === 'function' ? value(n, idx, array) : value
        return at ? [...c, n, newValue] : [...c, n]
    } , [])
const idOddIndex = n => n % 2
const isNth = nth => n => n % nth === nth - 1
const increment = n => n + 1

console.log(concatAt([0, 1, 3, 4, 6], idOddIndex, increment)) // [0, 1, 2, 3, 4, 5, 6]
concatAt([0, 1, 3, 4, 6], isNth(3), increment) // [0, 1, 3, 4, 4, 6]

我希望它能帮助别人。