Clone object (avoid mutation) - Javascript

clone-object.js

// https://scotch.io/bar-talk/copying-objects-in-javascript
private clone(obj) {
    let copy;

    // Handle the 3 simple types, and null or undefined
    if (null == obj || "object" != typeof obj) return obj;

    // Handle Date
    if (obj instanceof Date) {
      copy = new Date();
      copy.setTime(obj.getTime());
      return copy;
    }

    // Handle Array
    if (obj instanceof Array) {
      copy = [];
      for (let i = 0, len = obj.length; i < len; i++) {
        copy[i] = this.clone(obj[i]);
      }
      return copy;
    }

    // Handle Object
    if (obj instanceof Object) {
      copy = {};
      for (let attr in obj) {
        if (obj.hasOwnProperty(attr)) copy[attr] = this.clone(obj[attr]);
      }
      return copy;
    }

    throw new Error("Unable to copy obj! Its type isn't supported.");
  }

Link with other examples:
https://scotch.io/bar-talk/copying-objects-in-javascript