How to correctly define a variable to correct object scope

Question

myvar = whatever;

namespace.myspace.Create = function () {
    this.myvar = null;
    this.MyFunction = function (val) {
        this.myvar = val;
    }
}

---

namespace.myspace.Create = function () {
    var myvar = null;
    this.MyFunction = function (val) {
        this.myvar = val;
    }
}

---

namespace.myspace.Create = function () {
    myvar = null;
    this.MyFunction = function (val) {
        this.myvar = val;
    }
}

var myObject = new namespace.myspace.Create();

Looking at the above code, especially the myvar being defined as:

this.myvar = null;
var myvar = null;
myvar = null;

What are the main differences, scopes and uses of these? Any pitfalls or preferred ways of doing? Any of these just flat out wrong and should not be used?

myvar = whatever global. this.myvar = null context or instance. var myvar = null local. myvar = null global. — elclanrs
– elclanrs, Commented Sep 26, 2013 at 8:55
Which one you'd use depends on what you're trying to achieve. Note that all three of your examples set an instance variable with this.myvar inside this.MyFunction(). — nnnnnn
– nnnnnn, Commented Sep 26, 2013 at 8:55

Praind · Accepted Answer · 2013-09-26 08:57:08Z

1

myvar is a global variable

this.myvar is a public variable scoped on the myspace namespace

and var myvar is a private variable that is also scoped on the myspace namespace

answered Sep 26, 2013 at 8:57

Praind

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