声明后访问对象内的javascript属性

Question

I am trying to make a class in javascript.

define(['knockout', 'knockout-validation', 'jquery'], function(ko, validation, $) {
    var SignUpViewModel = {
        name: ko.observable().extend({
            required: true
        }),
        email: ko.observable().extend({
            required: true,
            email: true
        }),
        password: ko.observable().extend({
            required: true
        }),
        confirmPassword: ko.observable().extend({
            areSame: {
                params: password,
                message: "Repeat password must match Password"
            }
        }), // this line contains error . 
        register: function() {}
    }
    return SignUpViewModel;
});

Now its giving undefined error at password

Thanks in advance.

Answer 1

You haven't said how you're calling callitfunction , but if it's like this:

mytestobj.callitfunction();

...then this.password will be defined within the call.

console.log("The password is " + this.password()); // Since password is a KO observable, it's a function, so use () on it

Alternately, as that's a one-off object, just use mytestobj.password . Eg:

console.log("The password is " + mytestobj.password());

...and then you're not relying on this .

Note that this within a JavaScript function call is determined primarily by how the function is called , rather than where the function is defined as in some other languages. So for instance, this will not be mytestobj here:

var f = mytestobj.callitfunction;
f(); // `this` is not `mytestobj` within the call

More:

• Mythical methods

Answer 2

Object literals are not really optimal for Class creation. But they are a powerful tool, you can do it like this

(function(app) {
    app.define = function (definition) {
        definition.prototype = definition.prototype || {};
        definition.init.prototype = definition.prototype;
        definition.init.prototype.constructor = definition.init;

        return definition.init;
    };

})(window.app = window.app || {});

Use it like

app.define({
   init: function() {
        this.password = ko.observable().extend({ required: true });

        this.confirmPassword = ko.observable().extend({
            areSame: {
                params: this.password,
                message: "Repeat password must match Password"
            }
        });
   },
   prototype: {
      register: function() {
      }
   }
});

http://jsfiddle.net/ak2Ej/