How to replace substring in a string

Question

I have a string (i.e If you ask the makers of paper products, they will tell you that to be Agile you need to write ...) and the search terms (i.e ['makers', 'to be Agile']).

I expect this result If you ask the makers of paper products, they will tell you that to be Agile you need to write ...

I implement that with this method but sometimes doesn't work correctly.

private emphasize(text: string, highlights: string[]) {
    return highlights
      .filter(highlight => text.includes(highlight))
      .map(highlight => highlight.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&'))
      .reduce((txt, highlight) => {
        return txt.replace(new RegExp(highlight, 'gi'), '<strong>$&</strong>');
      }, text);
  }

Ori Drori · Accepted Answer · 2020-05-29 08:54:17Z

1

Create a RegExp by joining the highlights with the pipe | symbol, and wrapping with word boundaries (\b). Now use String.replace() to wrap found strings with . This will wrap entire expressions (to be Agile) with .

function emphasize(text, highlights) {
  const pattern = new RegExp(`\\b${highlights.join('|')}\\b`, 'gi');

  return text.replace(pattern, '<strong>$&</strong>');
}

const text = 'If you ask the makers of paper products, they will tell you that to be Agile you need to write';
const highlights = ['makers', 'to be Agile'];

const result = emphasize(text, highlights);

console.log(result);

If you really want single words, join the highlights with spaces, then split by spaces and join again with the pipe symbol:

function emphasize(text, highlights) {
  const pattern = new RegExp(`\\b${highlights.join(' ').split(' ').join('|')}\\b`, 'gi');

  return text.replace(pattern, '<strong>$&</strong>');
}

const text = 'If you ask the makers of paper products, they will tell you that to be Agile you need to write';
const highlights = ['makers', 'to be Agile'];

const result = emphasize(text, highlights);

console.log(result);

answered May 29, 2020 at 8:54

Ori Drori

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1 Comment

Wiktor Stribiżew Over a year ago

You should warn OP of the caveats related to word boundary usage. It won't work if the keywords start/end with special chars, like ['C++', '.NET code']

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