unist-util-reduce

unist-util-reduce

unist utility to recursively reduce a tree

Install

npm:

npm install unist-util-reduce

Usage

const u = require("unist-builder");
const reduce = require("unist-util-reduce");
const assert = require("assert");

const tree = u("tree", [
  u("leaf", "1"),
  u("node", [u("leaf", "2")]),
  u("void"),
  u("leaf", "3")
]);

const newTree = reduce(tree, function(node) {
  if (node.value === "2") {
    const duplicateNode = { ...node, value: "two" };
    return [duplicateNode, node];
  }
  return node;
});

const expected = u("tree", [
  u("leaf", "1"),
  u("node", [u("leaf", "two"), u("leaf", "2")]),
  u("void"),
  u("leaf", "3")
]);

assert.deepEqual(newTree, expected);

NOTE: leaf with value 2 is visited before it's parent node. By the time your transform function is invoked, it's children will already have been passed through transform.

API

reduce(tree, transform)

• tree - A node of type Parent
• transform - A function with the signature:
  • (node: Node, path: number[], root: Paretn) => Node | Node[]
    • node - The Node in the tree to be transformed
    • path - The path to reach this node in each level of the tree
    • root - The Parent root node
    • Returns - What you return is passed to .concat() on the children array of the node's parent.

Related

• unist-util-filter — Create a new tree with all nodes that pass a test
• unist-util-map — Create a new tree with all nodes mapped by a given function
• unist-util-remove — Remove nodes from a tree that pass a test
• unist-util-select — Select nodes with CSS-like selectors

License

MIT © Callum Macdonald / GeneroUS Labs