How to break up string based on specific length after finding the whitespace nearest to the character limit?

Question

I have to break up a string field into multiple string fields if the original string exceeds a specific character limit. The original string can be of different lengths but the additional fields like string2, and string3 have a max character length of 10.

Question:

1. How can I break up a single string field into multiple string fields with defined character limits based on the nearest whitespace to the character limit?

Example:

1. Hello world, how are you doing?

Assumptions:

• originalString can be of different string lengths
• string1 is maxed at 15 characters
• string2 is maxed at 10 characters
• string3 is maxed at 10 characters
• first 15 characters for the originalString would be Hello world, ho
• next 10 characters would be w are you
• next 10 character would be doing?
• Do not break up whole words
• only populate street2 and street3 if required. if all characters can fit into street1 and street2 then street3 can be empty

What I tried that didn't work:

let originalString = `Hello world, how are you doing?`
if(originalString.length > 15) {
  let string1 = originalString.substring(0,15) // this returns `Hello World,`
  let string2 = ???? // stuck here - need help
  let string3 = ???? // stuck here - need help
}

Expected output:

• originalString = Hello world, how are you doing?
• string1 = Hello world,
• string2 = how are
• string3 = you doing?

Answer 1

The following will get you what you want:

• the first string containing up to 15 characters
• the second string containing up to 10 characters
• the third string containing up to 10 characters

The breaks will only be done before whitespace characters and never inside a word.

const originalString = `Hello world, how are you doing?`,
      res=originalString.match(/(.{1,15})\s+(.{1,10})\s+(.{1,10})(?:\s+.|$)/);
console.log(res.slice(1));

Answer 2

I solved this by separating the original string into separate words and incrementally checking the length as I built each string. It works with your example, but could fail if there were some longer words or other written language quirks. I created an array, strings to build each string and indicate its maximum length.

let originalString = `Hello world, how are you doing?`;
let strings = [
    {len:15,string:""},
  {len:10,string:""},
  {len:10,string:""}
];
let originalStringArray = originalString.split(" ");
if(originalString.length > 15) {
    
  let osa_index = 0;
  for (let s = 0; s < strings.length; s++) {
    let proposedString = proposeNewString(s,osa_index);
    
      while (proposedString.length <= strings[s].len) {
        strings[s].string = proposedString;
        osa_index++;
        proposedString = proposeNewString(s,osa_index);
      }
  }
}



console.log(strings.map(s => s.string));

function proposeNewString(s,idx) {
    return (strings[s].string + ' ' + originalStringArray[idx]).trim();
}

Answer 3

I haven't tested it for different strings and different line lengths, but you could start from here...

let indices = [];

function getClosest(goal) {
    let find = goal;
    let index;
    let foundAtKey;

    indices.every(function(indice, key){
        if (indice < find && indices[key+1] > find) {
            index = indice;
            foundAtKey = key;

            return false;
        }

        return true;
    });

    indices = indices.slice(foundAtKey + 1);
    indices.forEach(function(value,key){
        indices[key] = value - index;
    });
    return index;
}

function splitString(myString = "Hello world, how are you doing?", indexes = [15, 10, 10]) {
    let myStringArray = [];

    for(let i=0; i < myString.length; i++) {
        if (myString[i] === " ") indices.push(i);
    }

    indexes.forEach(function(index){
        let closest = getClosest(index);

        if(typeof index !== 'undefined'){
            myStringArray.push(myString.substring(0, closest));
            myString = myString.substring(closest);
        } else {
            myStringArray.push(myString);
        }
    });

    return myStringArray;
}

const resultStringArray = splitString(); // or splitString("Hello world, how are you doing?", [15, 10, 10])
console.log(resultStringArray);