S1: new operator

Function shape (type) {This. type = type | "rect"; this. calc = function () {return "calc," + this. type ;}} var triangle = new shape ("Triangle"); print (triangle. calc (); var Circle = new shape ("circle"); print (circle. calc (); // The running result is as follows: calc, trianglecalc, circle

In JavaScript, the new operator is used to interact with a function. In essence, this action occurs:
First, create an empty object. Then, use the apply method of the function to pass the empty object as the first parameter of apply and the context parameter. In this way, this inside the function will be replaced by this empty object:

VaR triangle = new shape ("Triangle"); // the previous sentence is equivalent to the following code var triangle ={}; shape. Apply (triangle, ["Triangle"]);