TypeScript: Convert any to string

anyToString.ts

function anyToString(a: any): string {
  if (Array.isArray(a)) {
    let s = '[';
    const arr = a as Array<any>;
    const numberOfElements = arr.length;
    arr.map((e, index) => {
      let eString = anyToString(e);
      s = s + eString;
      if (index + 1 < numberOfElements) {
        s = s + ',';
      }
    });
    s = s + ']';
    return s;
  } else if (typeof a === 'object') {
    let s = '{';
    const o = a as object;
    const entries = Object.entries(o);
    const numberOfEntries = entries.length;
    entries.map(([k, v], index) => {
      let vString = anyToString(v);
      s = s + `"${k}":${vString}`;
      if (index + 1 < numberOfEntries) {
        s = s + ',';
      }
    });
    s = s + '}';
    return s;
  } else {
    switch (typeof a) {
      case 'function':
        return '[function]';
      case 'symbol':
        return '[symbol]';
      case 'string':
        return `"${a}"`;
    }
  }
  return `${a}`;
}