Function countChildren

packages/react/src/ReactChildren.js:383–390

* Count the number of children that are typically specified as * `props.children`. * * See https://reactjs.org/docs/react-api.html#reactchildrencount * * @param {?*} children Children tree container. * @return {number} The number of children.

(children: ?ReactNodeList)

 * @return {number} The number of children.
 */
function countChildren(children: ?ReactNodeList): number {
  let n = 0;
  mapChildren(children, () => {
    n++;
    // Don't return anything
  });
  return n;
}

type ForEachFunc = (child: ?React$Node) => void;