For example, what is the difference between target = Object(target) and target = Object() or target = new Object()?

if (typeof Object.assign != 'function') { Object.assign = function(target) { 'use strict'; if (target == null) { throw new TypeError('Cannot convert undefined or null to object'); } target = Object(target); for (var index = 1; index < arguments.length; index++) { var source = arguments[index]; if (source != null) { for (var key in source) { if (Object.prototype.hasOwnProperty.call(source, key)) { target[key] = source[key]; } } } } return target; }; }