Incomplete but browser compatible edn parsr

edn.js

class EDNParser {
  constructor(ednString) {
    this.edn = ednString;
    this.index = 0;
  }

  parse() {
    this.skipWhitespace();
    const element = this.readElement();
    this.skipWhitespace();
    if (this.index < this.edn.length) {
      throw new Error("Unexpected data after valid EDN element.");
    }
    return element;
  }

  readElement() {
    this.skipWhitespace();
    const char = this.peek();
    if (char === undefined) return null;
    switch (char) {
      case '"': return this.readString();
      case '{': return this.readMap();
      case '[': return this.readVector();
      case '(': return this.readList();
      case '#': return this.readTaggedOrSet();
      case ':': return this.readKeyword();
      case ';': this.skipComment(); return this.readElement();
      default:
        if (/\d|-|\+/.test(char)) return this.readNumber();
        if (/\\/.test(char)) return this.readCharacter();
        return this.readSymbol();
    }
  }

  readString() {
    this.expect('"');
    let str = "";
    while (this.peek() !== '"') {
      if (this.peek() === "\\") {
        this.index++;
        const escapeChar = this.edn[this.index];
        const escapeMap = { t: "\t", r: "\r", n: "\n", '\\': "\\", '"': '"' };
        str += escapeMap[escapeChar] || escapeChar;
      } else {
        str += this.edn[this.index];
      }
      this.index++;
    }
    this.expect('"');
    return str;
  }

  readCharacter() {
    this.expect("\\");
    const char = this.edn.slice(this.index).match(/^[^\s]+/);
    if (!char) throw new Error("Invalid character.");
    this.index += char[0].length;
    const charMap = { newline: "\n", return: "\r", space: " ", tab: "\t" };
    return charMap[char[0]] || char[0];
  }

  readSymbol() {
    const match = this.edn.slice(this.index).match(/^[^\s\(\)\[\]\{\}"#:;]+/);
    if (!match) throw new Error("Invalid symbol.");
    this.index += match[0].length;
    return match[0];
  }

  readKeyword() {
    this.expect(":");
    const match = this.edn.slice(this.index).match(/^[^\s\(\)\[\]\{\}"#:;]+/);
    if (!match) throw new Error("Invalid keyword.");
    this.index += match[0].length;
    return `:${match[0]}`;
  }

  readNumber() {
    const match = this.edn.slice(this.index).match(/^-?\d+(\.\d+)?([eE][+-]?\d+)?[M]?/);
    if (!match) throw new Error("Invalid number.");
    this.index += match[0].length;
    return parseFloat(match[0]);
  }

  readList() {
    this.expect("(");
    const list = [];
    while (this.peek() !== ")") {
      list.push(this.readElement());
    }
    this.expect(")");
    return list;
  }

  readVector() {
    this.expect("[");
    const vector = [];
    while (this.peek() !== "]") {
      vector.push(this.readElement());
    }
    this.expect("]");
    return vector;
  }

  readMap() {
    this.expect("{");
    const map = {};
    while (this.peek() !== "}") {
      const key = this.readElement();
      const value = this.readElement();
      map[key] = value;
    }
    this.expect("}");
    return map;
  }

  readTaggedOrSet() {
    this.expect("#");
    if (this.peek() === "{") return this.readSet();
    const tag = this.readSymbol();
    const element = this.readElement();
    return { tag, element };
  }

  readSet() {
    this.expect("{");
    const set = new Set();
    while (this.peek() !== "}") {
      set.add(this.readElement());
    }
    this.expect("}");
    return set;
  }

  skipComment() {
    while (this.peek() && this.peek() !== "\n") {
      this.index++;
    }
    this.index++; // Skip the newline
  }

  skipWhitespace() {
    while (/\s|,/.test(this.peek())) this.index++;
  }

  peek() {
    return this.edn[this.index];
  }

  expect(char) {
    if (this.edn[this.index] !== char) {
      throw new Error(`Expected '${char}' but found '${this.edn[this.index]}'.`);
    }
    this.index++;
  }
}

// Example usage:
const ednStr = `{:name "John", :age 0, :hobbies ["reading" "cycling"]}`;
const parser = new EDNParser(ednStr);
console.log(parser.parse());

output =

Object { ":name": "John", ":age": 0, ":hobbies": (2) […] }​