CODEWITHSUNDEEP
javascriptarrays
Cena
Cena

Reputation: 69

How Create more empty data in the Array?

I have 2 arrays as shown, now I want the less data array (specifically 2) to have the same amount as the 2 arrays above (23), how should I handle it?

enter image description here

The result I want should look something like this

[1,2,3,4,5,6,7,8,9,10]
["","","","",5,6,7,8,9,10]

thanks for help

Upvotes: 0

Views: 88

Answers (4)

KooiInc
KooiInc

Reputation: 122916

A simple loop should do the trick

let arr1 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
let arr2 = [5, 6, 7, 8, 9, 10];

while (arr2.length < arr1.length) {
  arr2.unshift("");
}

console.log(`arr1.length: ${arr1.length}, arr2.length: ${arr2.length}\n${
  JSON.stringify(arr1)}\n${JSON.stringify(arr2)}`);

// more generic
// a function to compare lengths of 2 arrays and insert spaces into
// the shortest array until its length equals the longest
const makeEqualLength = (arr1, arr2, clone) => {
  [arr1, arr2] = clone ? [arr1.slice(), arr2.slice()] : [arr1, arr2];
  const [longer, shorter] = arr1.length < arr2.length ? [arr2, arr1] : [arr1, arr2];
  
  while(shorter.length < longer.length) {
    shorter.unshift("");
  }

  return [arr1, arr2];
};

arr1 = [...Array(10)].map(() => Math.floor(Math.random() * 42));
arr2 = [...Array(3)].map(() => Math.floor(Math.random() * 42));
const [newArr1, newArr2] = makeEqualLength(arr1, arr2, true);
//                         └─ use function             │
//                                                     └─ original arrays unchanged
console.log(`newArr1.length: ${newArr1.length}, newArr2.length: ${newArr2.length}\n${
  JSON.stringify(newArr1)}\n${JSON.stringify(newArr2)}`);

Upvotes: 2

Owen Kelvin
Owen Kelvin

Reputation: 15083

You can create a new array and merge the two arrays

let arr1 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
let arr2 = [5, 6, 7, 8, 9, 10];

arr2 = [...Array(arr1.length - arr2.length).fill(""), ...arr2]


console.log(`arr1.length: ${arr1.length}, arr2.length: ${arr2.length}\n${
  JSON.stringify(arr1)}\n${JSON.stringify(arr2)}`);

Upvotes: 1

vazsonyidl
vazsonyidl

Reputation: 471

If you want to fill the start of the array, maybe the following would help you out:

Array(array1.length - array2.length).fill('').concat(array2);

Please answer if you need more help than this as your question is not a 100% clear now.

Upvotes: 1

T.J. Crowder
T.J. Crowder

Reputation: 1074475

You can insert entries into an array via splice:

const diff = bigger.length - smaller.length;
if (diff > 0) {
    smaller.splice(0, 0, ...Array(diff).fill(""));
}

Live Example:

const bigger = [1,2,3,4,5,6,7,8,9,10];
const smaller = ["y", "z"];

const diff = bigger.length - smaller.length;
if (diff > 0) {
    smaller.splice(0, 0, ...Array(diff).fill(""));
}

console.log("Result:");
console.log(JSON.stringify(bigger));
console.log(JSON.stringify(smaller));

Or create a new array with the necessary additional entries:

const diff = bigger.length - smaller.length;
if (diff > 0) {
    smaller = [...Array(diff).fill(""), ...smaller];
}

Live Example:

const bigger = [1,2,3,4,5,6,7,8,9,10];
let smaller = ["y", "z"];

const diff = bigger.length - smaller.length;
if (diff > 0) {
    smaller = [...Array(diff).fill(""), ...smaller];
}

console.log("Result:");
console.log(JSON.stringify(bigger));
console.log(JSON.stringify(smaller));

Upvotes: 2

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