Slice an array index wise and push into empty array-CodePudding

I have 2 arrays. one of them(config) decides how many elements are going to be pushed in new array(finalData) from existing array(items).

I tried to use slice but at the 3rd index the value is duplicated from the 2nd index. Try to run code and you'll get the idea. Here's my sandbox

Desired output is that I get an array of arrays split exactly by using config indexes.

const config = [1,2,1, 2];
const items = ["one", "two", "three", "four", "five", "six", "seven", "eight"];

const finalData = []

for (let i = 0; i < items.length; i  ) {
  if(config[i] !== undefined) { 
  finalData.push(items.slice(i, config[i]   i))
  } else {
    finalData.push([items[i]])
  }
}

console.log(finalData);

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CodePudding user response：

I would suggest iterating through the config array instead of the items array

const config = [1, 2, 1, 2];
const items = ["one", "two", "three", "four", "five", "six", "seven", "eight"];

const finalData = [];
let index = 0;
for (let size of config) {
  finalData.push(items.slice(index, index   size));
  index  = size;
}
// then collect any remaining
while (index < items.length) {
  finalData.push([ items[index  ] ]);
}

console.log(JSON.stringify(finalData));

If the length items can be shorter than the defined config, you may need to add some checks in to prevent empty arrays from being added to final data

CodePudding user response：

You can use map() with splice() to get the items from items array with the amount config provides.

If after the map, there are still items in the items array, use another map() to add those

const config = [1,2,1, 2];
const items = ["one", "two", "three", "four", "five", "six", "seven", "eight"];

let finalData = config.map(n => items.splice(0, n))

if (items.length > 0) {
  finalData = [ ...finalData, ...items.map(i => [ i ]) ];
}

console.log(finalData);

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[
  [
    "one"
  ],
  [
    "two",
    "three"
  ],
  [
    "four"
  ],
  [
    "five",
    "six"
  ],
  [
    "seven"
  ],
  [
    "eight"
  ]
]

CodePudding user response：

You could iterate through config array and use .splice(0, qty). Since .splice() mutates the array, if it called on every iteration, the first parameter is 0 index by default.

Details are commented in example

const group = [1, 2, 1, 2];
const items = ["one", "two", "three", "four", "five", "six", "seven", "eight"];

// >ext< = 8 - [1   2   1   2] /* returns 2 */
const ext = items.length - group.reduce((sum, add) => sum   add);

// >cfg< = [1, 2, 1, 2] merge with [1, 1]
const cfg = config.concat(Array(ext).fill(1));

// >qty< = [1, 2, 1, 2, 1, 1] returns [["one"], ["two", "three"],...]
const dat = cfg.flatMap(qty => [items.splice(0, qty)]);

console.log(dat);

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