JavaScript：查找字符串中所有出现的子字符串索引

Question

I need to write a function that is going to take a string and an array of substrings. and I need to add some HTML tag to wrap the substrings in the string. If two such substrings overlap, I should wrap them together with only one pair of tag.

The first thing I need to do is to get the start indices and end indices of where a substring occurs in the string. For example:

const str = 'aabc'
const target = ['aa', 'bc']

I need to be able to know that the indices for the substrings are [[0,2], [2,4]] where the start index is inclusive and the end index is exclusive.

Here is my attempt

function findOccurrances(str, words) {
  return words.map((word) => [
    str.indexOf(word),
    str.indexOf(word) + word.length,
  ])
}

However, if target is ['a', 'bc'] , the result should be [[0, 1], [1,2], [2,4] but since indexOf only returns the first occurrence of the substring, we only get [[0, 1], [2,4] as the result using my function.

I wonder what are some ways to achieve this?

Answer 1

Seems about right

 const str = 'aabc' const target = ['aa', 'bc'] function findOccurances(str, words) { const list = [] str.split('').forEach((c,i) => { words.forEach(t => { if (str.substr(i, t.length) === t) { list.push([i, i + t.length]) } }) }) return list } console.log(findOccurances(str, target))

Answer 2

You could combine reduce with another recursive inner function and in each call pass remaining word text.

 function findOccurrances(str, words) { const f = (word, rest, last = 0) => { const result = [] const index = rest.indexOf(word) if (index.= -1) { result,push([last + index. last + index + word.length]) result.push(..,f(word. rest,slice(index + 1); last + index + 1)) } return result. } return words,reduce((r. e) => { r.push(..,f(e; str)) return r, }. []) } console,log(findOccurrances('aabc', ['a'. 'bc'])) console,log(findOccurrances('aabc', ['bc'. 'aa'])) console,log(findOccurrances('azzz', ['zz']))

Answer 3

Created a String.stringIndex method which takes a substring as parameter, finds the start and end index of substring in the parent string. Finally, returning an array of start and end indexes. Using this method i created a function which you can use to get the results as you expect !

 String.prototype.stringIndex = function(t) {
    t = Array.from(t);
    let start_index = this.indexOf(t[0]);
    let end_index = this.slice(start_index + 1, this.length);
    if (t.length == 1) {
      end_index = start_index;
    } else {
      let increment = start_index + 1 ;
      end_index = end_index.indexOf(t[t.length - 1]) + increment;
    }
    return [start_index,
      end_index];
  }

  function findOccurrances(string, words) {
    return words.map((word) => string.stringIndex(word));
  }

  console.log(findOccurrances("i love chocolates", ["love", "chocolates"]));