Truncate string after the cutting word in Javascript

Question

I want to truncate a string after certain characters length in javascript. When the character length is reached then string should not be cut in the middle of the word rather it should complete the word and then truncate the string. What I have tried uptil now cuts the string before the cutting word. I want to include the cutting word in returned string. Here is my code:

function truncateString(yourString, maxLength) {
  var trimmedString = yourString.substr(0, maxLength);
  trimmedString = trimmedString.substr(0, Math.min(trimmedString.length, trimmedString.lastIndexOf(" ")));
  return trimmedString;
}

now when I call this function on with following parameters:

truncateString('The quick brown fox jumps over the lazy dog',6)

The output is 'The' rather than 'The quick.

Please point out what I need to change. Thanks

Answer 1

You can search for the index of immediate space after the maxLength by using the second parameter of indexOf

function truncateString(yourString, maxLength) {
  // get the index of space after maxLength
  const index = yourString.indexOf(" ", maxLength);
  return index === -1 ? yourString : yourString.substring(0, index)
}

const str = 'The quick brown fox jumps over the lazy dog';

console.log(truncateString(str,6))
console.log(truncateString(str,10))
console.log(truncateString(str,100))

Answer 2

One alternative is using regex.

You can build a regex pattern based on the value passed to function.

^.{${value}}.*?\\b
       |     |_____________ expression to get value upto next word boundry
       |
       |___________________ Value passed to function

let trmStr = (input,value) => {
  let reg = `^.{${value}}.*?\\b`
  let regex = new RegExp(reg)
  return input.match(regex)
}

console.log(trmStr('The quick brown fox jumps over the lazy dog', 6))