deepEquals.js

function deepEquals(thing1, thing2) {
  let typeOfFun = (x) => (x) => (x == null ? "null" : typeof x);

  const type1 = typeOfFun(thing1);
  const type2 = typeOfFun(thing2);

  let isNull1 = type1 == "null";
  let isNull2 = type2 == "null";

  if (isNull1 && isNull2) {
    return true;
  } else if (isNull1 || isNull2 || type1 != type2) {
    return false;
  } else {
    switch (typeof thing1) {
      case "object":
        let keys1 = Object.keys(thing1);
        let keys2 = Object.keys(thing2);
        let s2 = new Set(keys2);

        let sameKeys =
          keys1.length == keys2.length &&
          keys1.reduce((acc, next) => acc && s2.has(next), true);

        let reducer = (acc, key) => acc && deepEquals(thing1[key], thing2[key]);
        return sameKeys && keys1.reduce(reducer, true);
        break;

      default:
        return thing1 == thing2;
    }
  }
}