JavaScript: get words and its indices in a sentence

user_621210 0
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I need to get all the words from a sentence and also their index position within the sentence. The same word can happen multiple times in the sentence.

I was trying to do this using the filter method but the index indicates the position in the array not the position within the sentence.

var sentence = "This is a short sentence, a demo sentence."

sentence.split(" ").filter((word, index) => {
    
}
javascript
3 Answers

You can use .reduce:

const sentence = "This is a short sentence, a demo sentence.";
let index = 0;
const nonAlphabeticWithoutSpace = /[^a-zA-Z ]/g;

const res = sentence.split(" ").reduce((acc, item) => {
  // get word without other characters
  const word = item.replace(nonAlphabeticWithoutSpace, "");
  // get prev indices of this word
  const wordIndices = acc[word];
  // create/update the indices list
  acc[word] = wordIndices ? [...wordIndices, index] : [index]; 
  // increment the index
  const nonAlphabetic = item.match(nonAlphabeticWithoutSpace);
  index += nonAlphabetic 
    ? word.length+nonAlphabetic.length+1 
    : word.length+1;
  return acc;
}, {});

console.log(res);

If you want to disregard case senstivity, use .toLowerCase().

user_74863130

Use map instead of filter, loop the array and find position by calculating the letter count.

...and also their index position within the sentence.

By index I assume the position at which the word starts in the sentence.

var sentence = "This is a short sentence, a demo sentence."
let position = 0;
// the words array
const wordsList = sentence.split(" ");

// get the word and position in sentence
const wordDetails = wordsList.map((word, index) => {
  // +1 to account for space
  position = index && wordsList[index - 1].length + position + 1;
  return {
    word,
    position
  };
});

console.log(wordDetails);

If you need a different output like { <word> : [pos1, pos2] } try below sample

var sentence = "This is a short sentence, a demo sentence."
let position = 0;
// the words array
const wordsList = sentence.split(" ");
let wordDetails = {};

// get the word and position in sentence
wordsList.forEach((word, index) => {
  // +1 to account for space
  position = index && wordsList[index - 1].length + position + 1;

  // check if entry exists
  if (!wordDetails[word]) {
    wordDetails[word] = [];
  }

  // insert the position in array
  wordDetails[word].push(position)
});

console.log(wordDetails);

user_11883220 

  // below code will execute an object with key of
  // the index and value 
  
  const sentence = "This is a short sentence, a demo sentence."
        let result = {}
        sentence.split(" ").forEach((word, index) => {
            result = {
                ...result,
                [index]: word
            }
        })
        console.log(result)
        /*
        the result will be like below:
        {
            0: "This"
            2: "a"
            1: "is"
            4: "sentence,"
            3: "short"
            6: "demo"
            5: "a"
            7: "sentence."
        }
        */

user_83486950
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