I have an object written like this:
Object1.prototype = {
isInit: false,
Get : function (){}
}
Now I'd like to add a constructor which takes one parameter. How can I do it?
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5 Answers
Class declaration
var User = function(name, age) { // constructor
}
User.prototype = {}
Instance variables (members)
var User = function(name, age) {
this.name = name;
this.age = age;
}
User.prototype = {}
Static variables
var User = function(name, age) {
this.name = name;
this.age = age;
}
User.prototype = {
staticVar: 15,
anotherStaticVar: 'text'
}
Here I defined two static variables. Each User instance has access to these two variables. Note, that we can initialize it with value;
Instance functions (methods)
var User = function(name, age) {
this.name = name;
this.age = age;
}
User.prototype = {
getName: function() {
return this.name;
},
setName: function(name) {
this.name = name;
}
}
Usage example:
var user = new User('Mike', 29);
user.setName('John');
alert(user.getName()); //should be 'John'
Static functions
var User = function(name, age) {
this.name = name;
this.age = age;
}
User.create = function(name, age) {
return new User(name, age);
}
User.prototype = {}
3 Comments
Felix Kling
+1 But it is not really a class. JavaScript has no concept of classes.
Andrew Orsich
@Felix: I agree with you about javascript classes conceprt, it just i call it 'class'.
Assuming that by "ctor" you mean "constructor", in JavaScript that's just a function. In this case your constructor would need to be "Object1" itself - in other words, what you've got there makes sense if you have already defined "Object1" to be a function.
Thus,
function Object1(param) {
// constructor code
}
would be the constructor for your type.
Now there are some JavaScript libraries that provide a utility layer for defining classes. With those, you generally pass some sort of object (like you've got) that includes an "init" function. The libraries provide APIs for creating "classes" and for extending one class from another.
1 Comment
Pointy
Note (1 Jan 2019) — this answer is from 2011, and predates the ES2015
class declaration mechanism. The answer is still accurate, but modern code may by preference prefer the newer syntax.Javascript has prototype based object model. Check this mozilla wiki page and suddenly you'll feel much better in js land.
Comments
We can define a constructor in javaScript is same as we fine function, so constructor is just a function.
//function declaration
function func(){}
In case of Contructor We use initial letter in caps in construct like
//constructor
function Func(){}
now do whatever you want to with your constructor
var constructor1 = new Func();
Comments
class CLASS_NAME
{
private:
int variable;
public:
CLASS_NAME() //constructor
{
variable = 0;
}
};
3 Comments
Semicolons and Duct Tape
Muhammad welcome to SO. one line answers typically don't get to much attention around here. you could improve this answer by explaining what value it has for someone who is trying to figure out how to define a javascript constructor
Ro Yo Mi
Can you edit your proposed answer to expand on what this does and how it addresses the OP?
Muhammad Rehan
Dear I have given the basic example of constructor.