Function constrain

src/react-list.js:68–86

(props, state)

};

const constrain = (props, state) => {
  const { length, minSize, type } = props;
  let { from, size, itemsPerRow } = state;
  size = Math.max(size, minSize);
  let mod = size % itemsPerRow;
  if (mod) size += itemsPerRow - mod;
  if (size > length) size = length;
  from =
    type === 'simple' || !from ? 0 : Math.max(Math.min(from, length - size), 0);

  if ((mod = from % itemsPerRow)) {
    from -= mod;
    size += mod;
  }

  if (from === state.from && size === state.size) return state;

  return { ...state, from, size };
};

export default class ReactList extends Component {
  static displayName = 'ReactList';