Javascript calling prototype functions in constructor

I keep getting an error saying that my functions are not defined when I was trying to call the prototype functions in the constructor and I dont know whats wrong with it.

Here's the code I have:

function Renderer()
{
    initialiseWebGL();
    initialiseShader();
    initialiseBuffer();
}

Renderer.prototype.initialiseWebGL()
{
    //Do stuff.
};

Renderer.prototype.initialiseShader()
{
        //Do Shader's stuff
};

Renderer.prototype.initialiseBuffer()
{
        //Do Buffers
};

What is wrong with it?