Question

It works, I’ve tested it. What I want to know is – is this good practice. Obviously I could have just used an associative array and called it. But I wanted to encapuslate it into an object with state.

var View_message = function(div)
{    this.messages = 
    {
        empty: 'Please complete all fields',
        empty_bm: 'Please enter both a title and url',
        name: 'Only letters or dashes for the name field',
        email: 'Please enter a valid email',
        same: 'Please make emails equal',
        taken: 'Sorry that email is taken',
        pass: 'Please enter a valid password, 6-40 characters',
        validate: 'Please contact <a class="d" href="mailto:[e-mail]">support</a> to reset your password',
        url:  'Pleae enter a valid url'
    }; 
    this.div = div; 
}; 

View_message.prototype.display = function(type) 
{
    document.getElementById(this.div).innerHTML=this.messages[type];
};

obj_view = new View_message('test_id')
obj_view.display('empty');

Answer 1

You will be creating a copy of this.messages for each instance of View_message. To prevent that, you could store the messages in the prototype.

Also, you are doing a lookup of the div every time you display a message. I’d store a reference to the div in the constructor instead.

function View_message (div)
{
    this.div = document.getElementsById(div);
}

View_message.prototype.messages = {
    empty: 'Please complete all fields',
    empty_bm: 'Please enter both a title and url',
    name: 'Only letters or dashes for the name field',
    email: 'Please enter a valid email',
    same: 'Please make emails equal',
    taken: 'Sorry that email is taken',
    pass: 'Please enter a valid password, 6-40 characters',
    validate: 'Please contact <a class="d" href="mailto:[e-mail]">support</a> to reset your password',
    url:  'Pleae enter a valid url'
};
View_message.prototype.display = function(type)
{
    this.div.innerHTML = this.messages[type];
};