Better way to modify values in a single array to different format

Question

This may be a duplicate question. But I didn't find any similar questions in this forum.

I'm trying to modify values in an array to different format.

arrayInput = ['A', 'B', 'C', 'D', 'E', 'F'];

arrayOutput= ['A;B', 'C;D', 'E;F'];

I got the solution with the following approach

let arrayInput = ['A', 'B', 'C', 'D', 'E', 'F']
arrayOutput = [arrayInput[0]+';'+ arrayInput[1], arrayInput[2]+';'+ arrayInput[3]];
if (arrayInput[4]) {
     let val = arrayInput[4] + (arrayInput[5] ? ';'+arrayInput[5] : '');
     arrayOutput.push(val);
}
console.log(arrayOutput);

But I am looking for a generic solution such that even if I have more items in array, it should generate the output in desired format.

['A', 'B', 'C', 'D', 'E', 'F', 'G'] ==> ['A;B', 'C;D', 'E;F', 'G']
['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H'] ==> ['A;B', 'C;D', 'E;F', 'G;H']

Thanks for the support

Answer 1

You can use Array#reduce as in the following demo. Just in case there's an odd number of elements, I have included a test here ${arr[i+1] ? ";" + arr[i+1] : ""}; otherwise use ${arr[i+1]}, if you always have an even number of elements.

const arrayInput = ['A', 'B', 'C', 'D', 'E', 'F'],
      arrayOutput = arrayInput.reduce(
          (acc,cur,i,arr) => 
          i % 2 === 0 ? 
              [...acc,`${cur}${arr[i+1] ? ";" + arr[i+1] : ""}`] : 
              acc,
          []
      );

console.log( arrayOutput );
//OUTPUT: ['A;B', 'C;D', 'E;F'];

Answer 2

Use a for loop, and increment it by 2 every iteration:

const arrayInput = ['A', 'B', 'C', 'D', 'E', 'F', 'G'];

const res = [];
for (let i = 0; i < arrayInput.length; i += 2) {
  const part1 = arrayInput[i];
  const part2 = arrayInput[i + 1];
  if (part1) {
    res.push(part1 + (part2 ? (';' + part2) : ''));
  }
}
console.log(res);

Answer 3

You can try something like this (implementation based on array reduce and join):

const arrayInput = ['A', 'B', 'C', 'D', 'E', 'F'];

let temp = [];

const output = arrayInput.reduce((accumulator, item) => {
  if (temp.length < 2) {
    temp.push(item);
  } else {
    accumulator.push(temp.join(';'));
    temp = [];
  }
  return accumulator;
}, []);

console.log(output)

Answer 4

Using a foreach :

let arrayInput = ['A', 'B', 'C', 'D', 'E', 'F','G','H','I']
let newArray = [];

arrayInput.forEach((e,i) => {
  if((i + 1)%2==0)
  {
    newArray[newArray.length -1] = `${newArray[newArray.length -1]};${e}`
  }
  else
  {    
    newArray.push((i + 1) < newArray.length ? `${e};` : e)
  }
});

console.log(newArray)