taro-material/weapp/utils/slice.js

Mini Program components that implement Google's Material Design.

/**
 * Creates a slice of `array` from `start` up to, but not including, `end`.
 *
 * **Note:** This method is used instead of
 * [`Array#slice`](https://mdn.io/Array/slice) to ensure dense arrays are
 * returned.
 *
 * @since 3.0.0
 * @category Array
 * @param {Array} array The array to slice.
 * @param {number} [start=0] The start position. A negative index will be treated as an offset from the end.
 * @param {number} [end=array.length] The end position. A negative index will be treated as an offset from the end.
 * @returns {Array} Returns the slice of `array`.
 * @example
 *
 * var array = [1, 2, 3, 4]
 *
 * _.slice(array, 2)
 * // => [3, 4]
 */
function slice(array, start, end) {
  let length = array == null ? 0 : array.length;
  if (!length) {
    return [];
  }
  start = start == null ? 0 : start;
  end = end === undefined ? length : end;

  if (start < 0) {
    start = -start > length ? 0 : length + start;
  }
  end = end > length ? length : end;
  if (end < 0) {
    end += length;
  }
  length = start > end ? 0 : (end - start) >>> 0;
  start >>>= 0;

  let index = -1;
  const result = new Array(length);
  while (++index < length) {
    result[index] = array[index + start];
  }
  return result;
}

export default slice;