Slices of arrays in JavaScript

slices.js

function* makeSlices(delim, array) {
    let offset = 0;
    let length = 0;
    for(let x of array) {
        if (x === delim) {
            yield {
                offset,
                length,
                get: (i) => {
                  if (i < 0 || i > length) { throw "OutOfBounds"; }
                  return array[offset + i];
                },
                set: (i, newValue) => {
                  if (i < 0 || i > length) { throw "OutOfBounds"; }
                  array[offset + i] = newValue;
                }
            };
            offset = offset + length + 1;
            length = 0;
        } else {
            length++;
        }
    }
    yield { 
      offset,
      length,
      get: (i) => {
        if (i < 0 || i > length) { throw "OutOfBounds"; }
        return array[offset + i];
      },
      set: (i, newValue) => {
        if (i < 0 || i > length) { throw "OutOfBounds"; }
        array[offset + i] = newValue;
      }
    };
}

// increment every number the follows a 0
const array = [1, 0, 1, 2, 0, 3];
const iterator = makeSlices(0, array);
iterator.next();
for(let x of iterator) {
    x.set(0, x.get(0) + 1);
}
console.log(array);

// capitalise the first letter of each word
const string = "hello world".split("");
for(let substr of makeSlices(" ", string)) {
    substr.set(0, substr.get(0).toUpperCase());
}
console.log(string.join(""));