Question

I create portlets and there can be many instance of a portlet on a page, so that the functions and dom elements must be identified, AKA they must start with a particular namespace.

so that in some cases, I have to have my JS in a JSP page and cannot move it to a separate file, it is very inconvenient and hard to maintain.

a javascript in a JSP

var validator = new A.FormValidator({
        boundingBox: document.orderForm,

        validateOnBlur: true,
        validateOnInput: false,

        rules: {

            <portlet:namespace />significanceLevel: {
                digits: true                
            },

            <portlet:namespace />languageFrom: {
                required: true,
                notEqualTo: '#<portlet:namespace />languageTo'
            },

            <portlet:namespace />languageTo: {
                required: true,
                notEqualTo: '#<portlet:namespace />languageFrom'
            }
}
......

From <portlet:namespace />significanceLevel JSP generates _my_namespace_significanceLevel: .
Even if I pass myNamespace (from a JS in JSP – namespaces resolved on serverside) into a constructor, I cannot create myNamespace + ‘methodName’ in runtime

Namespace is only known on serverSide. So that one JS always has to be in a JSP page so that <portlet:namespace /> is resolved and all other JS objects have it accessible via constructor parameter for instance.

this is one workaround, but it cannot be used in many cases :

window[instance._method] = function() {
    instance.fileAddError.apply(instance, arguments);
};

where the name of _method was concatenated from string literals

Answer 1

It is easy to add dynamic properties to objects during runtime:

rules[namespace + 'significanceLevel'] = {digits: true};

So you could do something along the lines of:

var namespace = <portlet:namespace />;
var opts = {
    boundingBox: document.orderForm,
    validateOnBlur: true,
    validateOnInput: true,
    rules: {};
};
var addRule = function (name, rule) {
    opts.rules[namespace + name] = rule;
}

addRule('significanceLevel', {digits: true});
addRule('languageFrom', {...});
// etc...

var validator = new A.FormValidator(opts);