Simple Scriptable RSS Feed Parser (XML)

rss.js

function parseXML(string) {
  /*
   * Part 1
   *
   * Parse the xml into a DOM-like json
   *
   * Input: <tag attribute="value">text node<inline>text node</inline>text node</tag>
   *
   * Output:
   * {
   *   "name": "root",
   *   "children": [
   *     {
   *       "name": "tag",
   *       "attrs": {
   *         "attribute": "value"
   *       },
   *       "innerText": "text node text node",
   *       "children": [
   *         {
   *           "name": "inline",
   *           "attrs": {},
   *           "innerText": "text node",
   *           "children": []
   *         }
   *       ]
   *     }
   *   ]
   * }
   *
   */
  
  // Root of xml
  let main = {
    isRoot: true,
    name: "root",
    children: []
  }

  // Node to add onto
  let target = main

  // Store symbols to go back to parent nodes
  let goBack = {}
  
  // Declare the parser
  let parser = new XMLParser(string)

  // Store the new node and switch targets when entering a new tag
  parser.didStartElement = (name, attrs) => {
    let backTo = Symbol()
    goBack[backTo] = target
    let newTarget = {
      name,
      attrs,
      innerText: "",
      children: [],
      end: backTo
    }
    target.children.push(newTarget)
    target = newTarget
  }

  // Go back to the parent node when entering a closing tag
  parser.didEndElement = (name) => {
    let sym = target.end
    delete target.end
    target = goBack[sym]
  }

  // Add the inner text to the node, if there are multiple text nodes, combine them with spaces
  parser.foundCharacters = (text) => {
    target.innerText +=
      target.innerText === "" ? text.trim() : " " + text.trim()
  }

  // Throw error on invalid input
  parser.parseErrorOccurred = () => {
    console.warn(
      "A parse error occurred, ensure the document is formatted properly."
    )
  }

  // Parse and return the root
  parser.parse()

  // If something went wrong and there is no root node, throw an error
  if (!main.isRoot) {
    console.warn(
      "A parse error occurred, ensure the document is formatted properly."
    )
  }

  // Remove the isRoot key
  delete main.isRoot
  
  /*
   * Part 2
   *
   * Manipulate the AST-like json into a simpler json without attributes and other less important items. This will not collect both tag and text nodes if they are in the same tag.
   *
   * Input:
   * {
   *   "name": "root",
   *   "children": [
   *     {
   *       "name": "tag",
   *       "attrs": {
   *         "attribute": "value"
   *       },
   *       "innerText": "text node text node",
   *       "children": [
   *         {
   *           "name": "inline",
   *           "attrs": {},
   *           "innerText": "text node",
   *           "children": []
   *         }
   *       ]
   *     }
   *   ]
   * }
   *
   * Output:
   * {
   *   "tag": {
   *     "inline": "text node"
   *   }
   * }
   *
   * Notes: you can chose to only use part 1 if you need the attributes or text and tag nodes in the same tag. Replace the `return traverse(main)` below to `return main`
   */

  // Return the new simple JSON
  return traverse(main)

  // Function to change each node
  function traverse(node) {
    // Store the new node
    let newNode = {}

    // Repeat with all children nodes
    for (let child of node.children) {
      // traverse the child
      let newChild = traverse(child)

      // If there are no children of the child than it should become a text value
      if (child.children.length === 0) {
        newChild = child.innerText
      }

      // If the new node already has a key of the child's name it will become an array
      if (newNode[child.name]) {
        // If it is an array, push the new child
        if (Array.isArray(newNode[child.name])) {
          newNode[child.name].push(newChild)
        } else {
          // If it is not an array, change it into one
          newNode[child.name] = [newNode[child.name], newChild]
        }
      } else {
        // If it is not in the keys, set the child as a value in the new node
        newNode[child.name] = newChild
      }
    }

    // Return the new node
    return newNode
  }
}

Example

Input

<root>
  <node>
    <text>text node</text>
    <details>text node</details>
    <key>value</key>
  </node>
  <list>
    <item>text node</item>
    <item>text node</item>
    <item><tag>text node</tag></item>
    <key>value</key>
  </list>
</root>

Output

{
  "root": {
    "node": {
      "text": "text node",
      "details": "text node",
      "key": "value"
    },
    "list": {
      "item": [
        "text node",
        "text node",
        {
          "tag": "text node"
        }
      ],
      "key": "value"
    }
  }
}

List of RSS feeds

https://github.com/plenaryapp/awesome-rss-feeds