为什么函数在构造函数中声明时不使用new关键字？

Question

sample function declaration in function :

function Rectangle(height, width) {
  this.height = height;
  this.width = width;
  this.calcArea = function() {
      return this.height * this.width;
  };
  // put our perimeter function here!
  this.calcPerimeter = function() {
    return 2 * this.height + 2 * this.width;
};

sample new function declaration :

var actions = new function() {
    console.log("this is to do something");
}

Why are we using new keyword while declaring a new function but not using new keyword while declaring it in a constructor??

Answer 1

new is an operator. It allocates an object instance (and assigns it a prototype). The functions you create aren't instances of any sort of class, and are not going to be created in multiple copies. The static declaration defines the only instance that will exist.