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Javascript – How do I break a string into words and track the index of each word (within the original string)?

I have a string:

const str = 'a string, a long string'

I want to break it down into words (no problem here) and then track the index of each word within the original string.

Actual result:

[
  { word: 'a',      idx: 0 },
  { word: 'string', idx: 2 },
  { word: 'a',      idx: 0 },
  { word: 'long',   idx: 12 },
  { word: 'string', idx: 2 }
]

Desired result:

[
  { word: 'a',      idx: 0 },
  { word: 'string', idx: 2 },
  { word: 'a',      idx: 10 },
  { word: 'long',   idx: 12 },
  { word: 'string', idx: 17 }
]

Code so far:

const str = 'a string, a long string'

const segmenter = new Intl.Segmenter([], { granularity: 'word' })

const getWords = str => {
  const segments = segmenter.segment(str)
  return [...segments]
    .filter(s => s.isWordLike)
    .map(s => s.segment)
}

const words = getWords(str)

const result = words.map(word => ({
  word,
  idx: str.indexOf(word)
}))

console.log(result)
Tags:

3

Answers


  1. 0

    I decomposed your string into an array of object containing the word and the word index.

    const str = 'a string, a long string';

const words = str.split(' ').map((word, index) => ({ word, index }));

console.log(words)

    If you want the ponctuation as a word you could use a regex.

    const words = str.split(/s+|(?=p{P})|(?<=p{P})/u).map((word, index) => ({ word, index }));
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  2. 0

    The objects you’re iterating over, which contain the segment and whether or not it isWordLike, also have the index:

    const str = 'a string, a long string'

const segmenter = new Intl.Segmenter([], { granularity: 'word' })

const getWordsWithIndexes = str => {
  const segments = segmenter.segment(str)
  return [...segments]
    .filter(s => s.isWordLike)
    .map(s => ({ idx: s.index, word: s.segment }))
}

const result = getWordsWithIndexes(str)

console.log(result)

    Here’s the type definition:

    interface SegmentData {
    /** A string containing the segment extracted from the original input string. */
    segment: string;
    /** The code unit index in the original input string at which the segment begins. */
    index: number;
    /** The complete input string that was segmented. */
    input: string;
    /**
     * A boolean value only if granularity is "word"; otherwise, undefined.
     * If granularity is "word", then isWordLike is true when the segment is word-like (i.e., consists of letters/numbers/ideographs/etc.); otherwise, false.
     */
    isWordLike?: boolean;
}
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  3. 0

    Maybe an idea to use String.matchAll to retrieve words and indexes.

    Something like:

    const str = 'a string, a long string';
const x = 'astringalongstring';

console.log(getWordStartIndexes(str));
console.log(getWordStartIndexes(x));

function getWordStartIndexes(str) {
   const allMatches = str.matchAll(/(p{L}+?)([^p{L}]|[,:;]|$)/gu);
   return [...allMatches]
    .map( match => ({word: match[1], index: match.index }) )
   
}
    .as-console-wrapper {
    max-height: 100% !important;
}
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