string-punctuation-tokenizer/src/selectionHelpers.js

Small library that provides functions to tokenize a string into an array of words with or without punctuation

import {occurrencesInString} from './occurrences';
/**
 * Splice string into array of ranges, flagging what is selected
 * @param {String} string - string.
 * @param {Array} ranges - array of ranges [[int,int],...]
 * @return {Array} - array of objects [obj,...]
 */
export const spliceStringOnRanges = (string, ranges) => {
  let selectionArray = []; // response
  let remainingString = string;
  // shift the range since the loop is destructive by working on the remainingString and not original string
  let rangeShift = 0; // start the range shift at the first character
  ranges.forEach(function(range) {
    const firstCharacterPosition = range[0]-rangeShift; // original range start - the rangeShift
    const beforeSelection = remainingString.slice(0, firstCharacterPosition); // save all the text before the selection
    if (beforeSelection) { // only add to the array if string isn't empty
      selectionArray.push({text: beforeSelection, selected: false});
    }
    const shiftedRangeStart = range[0]-rangeShift; // range start - the rangeShift
    const shiftedRangeEnd = range[1]+1-rangeShift; // range end - rangeShift + 1 to include last character
    const selection = remainingString.slice(shiftedRangeStart, shiftedRangeEnd); // save the text in the selection
    const stringBeforeRange = string.slice(0, range[0]);
    const occurrence = occurrencesInString(stringBeforeRange, selection) + 1;
    const occurrences = occurrencesInString(string, selection);
    const selectionObject = {
      text: selection,
      selected: true,
      occurrence: occurrence,
      occurrences: occurrences,
    };
    selectionArray.push(selectionObject); // add the selection to the response array
    // next iteration is using remaining string
    const lastCharacterPosition = range[1]-rangeShift+1; // original range end position - the rangeShift + 1 to not include the last range character in the remaining string
    remainingString = remainingString.slice(lastCharacterPosition); // update the remainingString to after the range
    // shift the range up to last char of substring (before+sub)
    rangeShift += beforeSelection.length; // adjust the rangeShift by the length prior to the selection
    rangeShift += selection.length; // adjust the rangeShift by the length of the selection itself
  });
  if (remainingString) { // only add to the array if string isn't empty
    selectionArray.push({text: remainingString, selected: false});
  }
  return selectionArray;
};
/**
 * Converts ranges to array of selection objects
 * @param {String} string - text used to get the ranges of
 * @param {Array} selections - array of selections [obj,...]
 * @return {Array} - array of range objects
 */
export const selectionsToRanges = (string, selections) => {
  let ranges = []; // response
    selections.forEach( (selection) => {
      if (string && string.includes(selection.text)) { // conditions to prevent errors
        const splitArray = string.split(selection.text); // split the string to get the text between occurrences
        let beforeSelection = splitArray.slice(0, selection.occurrence);
        beforeSelection = beforeSelection.join(selection.text); // get the text before the selection to handle multiple occurrences
        const start = beforeSelection.length; // the start position happens at the length of the string that comes before it
        const end = start + selection.text.length - 1; // the end position happens at the end of the selection text, but length doesn't account for 0 based position start
        const range = [start, end]; // new range
        ranges.push(range); // add the new range
      }
    });
  return ranges;
};

export const selectionArray = (string, selections) => {
  let selectionArray = [];
  let ranges = selectionsToRanges(string, selections);
  selectionArray = spliceStringOnRanges(string, ranges);
  return selectionArray;
};