truncateStringAtWhitespace javascript Code Snippet in 2025

Truncates a string up to specified length, respecting whitespace when possible.

• Determine if String.prototype.length is greater or equal to lim. If not, return it as-is.
• Use String.prototype.slice() and String.prototype.lastIndexOf() to find the index of the last space below the desired lim.
• Use String.prototype.slice() to appropriately truncate str based on lastSpace, respecting whitespace if possible and appending ending at the end.
• Omit the third argument, ending, to use the default ending of '...'.

const truncateStringAtWhitespace = (str, lim, ending = '...') => {
  if (str.length <= lim) return str;
  const lastSpace = str.slice(0, lim - ending.length + 1).lastIndexOf(' ');
  return str.slice(0, lastSpace > 0 ? lastSpace : lim - ending.length) + ending;
};

truncateStringAtWhitespace('short', 10); // 'short'
truncateStringAtWhitespace('not so short', 10); // 'not so...'
truncateStringAtWhitespace('trying a thing', 10); // 'trying...'
truncateStringAtWhitespace('javascripting', 10); // 'javascr...'