Part of our (corporate) product is a Javascript API, we often hand copies of our (class) objects around and only want specific attributes exposed. Masquerade JS is a wrapper that attempts to correctly scope class methods and storage in OO Javascript. It allows you to expose only what you want to expose. There is a small caveat, if you pass references to the private this you will expose the entire object. If you want to stay protected only pass a reference to the public object provided to you on creation. The public object is briefly made available within the constructor on this.$public, be careful of circular references if you use it.
This adds class functionality to ES5, similar but not identical to ES6. However it adds private scoping to fields and methods which is not available in ES5 or ES6.
var Example = new Class({
construct:
function() {
this.count = 0;
this.string = 'example string';
}
}); var example = new Example();getString will be publicly callable.
var Example = new Class({
construct:
function() {
this.count = 0;
this.string = 'example string';
},
getString:
function() {
return this.string;
}
});
var example = new Example();
example.getString(); /* returns 'example string' */_incrementCount is only callable from the this context.
var Example = new Class({
construct:
function() {
this.count = 0;
this.string = 'example string';
},
getString:
function() {
this._incrementCount();
return this.string;
},
_incrementCount:
function() {
this.count++;
}
});
var example = new Example();
example._incrementCount(); /* undefined */
example.getString() /* returns 'example string' and increments this.count */getDate is copied by reference to the class definition.
var Example = new Class({
construct:
function() {
this.count = 0;
this.string = 'example string';
},
$getDate:
function() {
return (new Date()).getTime();
}
});
Example.getDate(); /* returns epoch */Extend will inherit all methods from Example.
var Extend = Example.extend({
construct:
function() {
this.count = 0;
this.string = 'extend string';
}
});
var extend = new Extend();
extend.getString() /* returns 'extend string' and increments this.count */getStringCount will only be available on instances of Extend.
var Extend = Example.extend({
construct:
function() {
this.count = 0;
this.string = 'extend string';
},
getStringCount:
function() {
return this.string + ' ' + this.count;
}
});
var example = new Example();
example.getStringCount(); /* undefined */
var extend = new Extend();
extend.getStringCount(); /* returns 'extend string *this.count' */Anything stored on this will be private to an instance.
var Example = new Class({
construct:
function() {
this.count = 0;
this.string = 'example string';
}
});
var example = new Example();
example.count; /* undefined */classPublic is copied by reference to the class definition and class instances.
var Example = new Class({
classPublic:
{
string: 'class public'
},
construct:
function() {
this.count = 0;
this.string = 'example string';
}
});
var example = new Example();
example.classPublic.string; /* 'class public' */
Example.classPublic.string; /* 'class public' */classStatic is copied by reference to the class definition.
var Example = new Class({
$classStatic:
{
string: 'class static'
},
construct:
function() {
this.count = 0;
this.string = 'example string';
}
});
var example = new Example();
example.classStatic.string; /* undefined */
Example.classStatic.string; /* 'class static' */_classPrivate is copied by reference to class instances.
var Example = new Class({
_classPrivate:
{
string: 'class private'
},
construct:
function() {
this.count = 0;
this.string = 'example string';
}
getClassPrivate:
function() {
return this._classPrivate.string;
}
});
var example = new Example();
var extend = new Extend();
example.classPublic.string; /* undefined */
Example.classPublic.string; /* undefined */
example.getClassPrivate(); /* returns 'class private' */
extend.getClassPrivate(); /* returns 'class private' */ string becomes a property on class instances.
var Example = new Class({
construct:
function() {
this.count = 0;
this.string = 'example string';
},
defineProperties:
{
string:
{
get:
function() {
return this.string;
}
}
}
});
var example = new Example();
example.string; /* 'example string' */The this referred to inside class functions is not the same as the constructed class object, but is an instance of the same class.
var Example = new Class({
construct:
function() {
this.count = 0;
this.string = 'example string';
},
getThis:
function() {
return this;
}
});
var example = new Example();
var privateExample = example.getThis();
example === privateExample /* false */
example instanceof Example /* true */
privateExample instanceof Example /* true */Class data storage will copy by reference during a Class.extend() if it is an object, but not if it is a scalar.
var Example = new Class({
scalar: '1234',
obj: {
value: 1234
},
obj2: {
value: 5678
}
});
var subClass = Example.extend({});
var example = new Example();
var sub = new subClass();
sub.scalar = 'abcd'; /* Updates only the subclass */
example.scalar === '1234' /* true */
sub.obj.value = 0; /* Updates by-reference */
example.obj.value === 0; /* true */
sub.obj2 = 'replace'; /* Replace by-reference copy */
example.obj2; /* `{value: 5678}` */