d3-dag/src/dag/eachBefore.js

Layout algorithms for visualizing directed acylic graphs.

// Call a function on each node such that a node is called before any of its children
export default function(func) {
  this.each((n) => (n._num_before = 0));
  this.each((n) => n.children.forEach((c) => ++c._num_before));

  const queue = this.roots();
  let node;
  let i = 0;
  while ((node = queue.pop())) {
    func(node, i++);
    node.children.forEach((n) => --n._num_before || queue.push(n));
  }

  this.each((n) => delete n._num_before);
  return this;
}