如何在Javascript中返回数组中的正确位置？

var widestPasture = function (landscape) {
    let answer = [0, 0, 0];
    for (let i = 0, start = 0; i < landscape.length; i++) {
        if (landscape[i] != "_") {
            start = i + 1;
        } else if (i + 1 - start >= answer[0]) {
            answer = [i + 1 - start, start, i];
        }
    }
    return answer;
};

console.log(widestPasture("_-___-__-____-______-_"));
// -> [6, 14, 19]
console.log(widestPasture("_-___-__-___-"));
// -> [3, 9, 11]

var widestPasture = function (landscape) {
  let array = landscape.split("-");
  let longest = Math.max(...(array.map(el => el.length)));
  let pos = array.lastIndexOf("_".repeat(longest));
  //reconstruct
  let c =0, firstIndex=0;
  while (c<pos) {
   firstIndex += array[c].length +1;
   c++;
   }
  let answer = [longest, firstIndex, firstIndex+longest-1];
  return answer;
};

console.log(widestPasture("_-___-__-____-______-_"));
// -> [6, 14, 19]
console.log(widestPasture("_-___-__-___-"));
// -> [3, 9, 11]

function getLastValidMatchingPastureData(value) {
  const lastValidPastureMatch = [...String(value).matchAll(/_+/g)]
    // sort each matching pasture data item ascending by `length`.
    .sort(([a], [b]) => a.length - b.length)
    // access/get the last matching item (the last longest item).
    .at(-1);

  return [ // assemble the data of OP's interest.
    lastValidPastureMatch[0].length,
    lastValidPastureMatch.index,
    lastValidPastureMatch.index + lastValidPastureMatch[0].length - 1,
  ];
}

console.log( // [3, 9, 11]
  '"_-___-__-___-" ... ',
  getLastValidMatchingPastureData("_-___-__-___-"),
);
console.log( // [6, 14, 19]
  '"_-___-__-____-______-_" ... ',
  getLastValidMatchingPastureData("_-___-__-____-______-_"),
);
console.log( // [6, 21, 26]
  '"_-___-__-______-____-______-_" ... ',
  getLastValidMatchingPastureData("_-___-__-______-____-______-_"),
);

.as-console-wrapper { min-height: 100%!important; top: 0; }

function widestPasture(input) {
    //At the very start we do not have a solution yet, do we default bestSofar to undefined
    let bestSofar = undefined;
    //lastStartIndex being negative means we are currently not inside a pasture
    let lastStartIndex = -1;
    //we loop the indexes of the string
    for (let i = 0; i < input.length; i++) {
        //we check whether the current character is outside of a pasture
        if (input[i] !== '_') {
            //if so, and we were in a pasture just before, then we found the end of
            //the current pasture at the previous index of i - 1
            if (lastStartIndex >= 0) {
                //we create a solution array in order to compare to the best so far
                let currentPasture = [i - lastStartIndex, lastStartIndex, i - 1];
                //if we did not have a best earlier, or the best so far is not
                //strictly worse than our current solution, then we replace bestSofar
                //with the currentPasture
                if ((!bestSofar) || (bestSofar[0] <= currentPasture[0])) bestSofar = currentPasture;
                //since we have left the pasture, we mark lastStartIndex with a negative
                //value so we will be aware that we are not inside a pasture
                lastStartIndex = -1;
            }
        //the else here means that the character is '_', so that we are inside a pasture
        } else if (lastStartIndex < 0) lastStartIndex = i;
    }
    //After the loop we check whether we were inside a pasture at the last character
    //to cover (literally) edge-cases
    if (lastStartIndex >= 0) {
        //We create the currentPasture array
        let currentPasture = [input.length - lastStartIndex, lastStartIndex, input.length - 1];
        //and compare it with the best so far and if it's better, then it will become
        //the new best
        if ((!bestSofar) || (bestSofar[0] <= currentPasture[0])) bestSofar = currentPasture;
    }
    return bestSofar;
}
console.log(widestPasture("_-___-__-____-______-_"));
// -> [6, 14, 19]
console.log(widestPasture("_-___-__-___-"));
// -> [3, 9, 11]
console.log(widestPasture("_-__-___"));
// -> [3, 5, 7]