Method getElementAtIndex

packages/react-devtools-shared/src/devtools/store.js:530–605

(index: number)

  }

  getElementAtIndex(index: number): Element | null {
    if (index < 0 || index >= this.numElements) {
      console.warn(
        `Invalid index ${index} specified; store contains ${this.numElements} items.`,
      );

      return null;
    }

    // Find which root this element is in...
    let root;
    let rootWeight = 0;
    for (let i = 0; i < this._roots.length; i++) {
      const rootID = this._roots[i];
      root = this._idToElement.get(rootID);

      if (root === undefined) {
        this._throwAndEmitError(
          Error(
            `Couldn't find root with id "${rootID}": no matching node was found in the Store.`,
          ),
        );

        return null;
      }

      if (root.children.length === 0) {
        continue;
      }

      if (rootWeight + root.weight > index) {
        break;
      } else {
        rootWeight += root.weight;
      }
    }

    if (root === undefined) {
      return null;
    }

    // Find the element in the tree using the weight of each node...
    // Skip over the root itself, because roots aren't visible in the Elements tree.
    let currentElement: Element = root;
    let currentWeight = rootWeight - 1;

    while (index !== currentWeight) {
      const numChildren = currentElement.children.length;
      for (let i = 0; i < numChildren; i++) {
        const childID = currentElement.children[i];
        const child = this._idToElement.get(childID);

        if (child === undefined) {
          this._throwAndEmitError(
            Error(
              `Couldn't child element with id "${childID}": no matching node was found in the Store.`,
            ),
          );