Method getIndexOfElementID

packages/react-devtools-shared/src/devtools/store.js:678–741

(id: number)

  }

  getIndexOfElementID(id: number): number | null {
    const element = this.getElementByID(id);

    if (element === null || element.parentID === 0) {
      return null;
    }

    // Walk up the tree to the root.
    // Increment the index by one for each node we encounter,
    // and by the weight of all nodes to the left of the current one.
    // This should be a relatively fast way of determining the index of a node within the tree.
    let previousID = id;
    let currentID = element.parentID;
    let index = 0;
    while (true) {
      const current = this._idToElement.get(currentID);
      if (current === undefined) {
        return null;
      }

      const {children} = current;
      for (let i = 0; i < children.length; i++) {
        const childID = children[i];
        if (childID === previousID) {
          break;
        }

        const child = this._idToElement.get(childID);
        if (child === undefined) {
          return null;
        }

        index += child.isCollapsed ? 1 : child.weight;
      }

      if (current.parentID === 0) {
        // We found the root; stop crawling.
        break;
      }

      index++;

      previousID = current.id;
      currentID = current.parentID;
    }

    // At this point, the current ID is a root (from the previous loop).
    // We also need to offset the index by previous root weights.
    for (let i = 0; i < this._roots.length; i++) {
      const rootID = this._roots[i];
      if (rootID === currentID) {
        break;
      }

      const root = this._idToElement.get(rootID);
      if (root === undefined) {
        return null;
      }