Question

Class.method = function () { this.xx }
Class.prototype.method = function () { this.xx }
var clazz = new Class();
clazz.method();

When I call the 4th line this in the function will refer to clazz
But when Class.method() is executed, what will this refer to?

Answer 1

this within the Class.prototype.method function will still refer to the Class instance. This isn’t a static method, a static (i.e. one per class) method would be something like:

Class.method = function () {
    // I am a static method
};

For example:

var Example = function () {
    this.name = "DefaultName";
};

Example.prototype.setName = function (name) {
    this.name = name;
}

var test = new Example();
test.setName("foo");

console.log(test.name); // "foo"