new function(...) { ... }


is (mostly) equivalent to


(function(...) { ... }) ()


(The function is defined and evaluated in-place, oftentimes to create private, closed-over data, and oftentimes to do a switch against the current browser or some other environment feature to determine what function you actually want to use later on, instead of constantly testing the environment every time you call that function.)

Evaluation in-place using parentheses is more efficient, but syntactically ugly, and it’s not clear until the very end that it’s being evaluated in-place. Using the new keyword is less efficient and less immediately obvious unless you’re familiar with the style, but its syntax is nicer and, assuming you’ve seen the style before, it’s clear up-front that the function is being defined and evaluated in-place.

So now I am able to rewrite someConstructor like this:

function someConstructor() {
[code]
return this.toObject();
}

Worked in my code, but not sure if this could have unforeseen consequences. Anyone has an idea about that?

var freshFunction = function(args,body) {
if (args.length>0) {
var sArgs = args.join(’,');
} else {
var sArgs = ”;
}
return Function(sArgs,body);
}

var fnFromString = function(fnStr) {
var f1 = f2 = fnStr.replace(/\n|\r/g,”),
f1a = (f1.split(/\{/i))[0],
f1b = (f1a.split(/\(/i))[1].replace(/\)/,”).trim();
if (f1b.length>0){
var fx = f1b.split(’,');
} else {
var fx = [];
}
// get function body
f2 = f2.replace(/(^function.+\{)(.+)(\}$)/i,”$2″);
return freshFunction(fx,f2);
}

(sorry, perhaps this is posted twice: I am not sure the post came trough, firefox told me the connection was reset after clicking the submit button.)

Couple of questions tho…
Firstly, without new (as you state) you are giving up the prototype object. But I thought one very real benefit of the prototype object is to assign methods to them once and have them shared by all, thus saving space. It seems your recommended obj literal notation requires the repeated inclusion of inline functions for every object created. I presume you consider this an acceptable trade off?

Secondly, how do you represent static variable/methods (public or private) without the use of new?

A tentative repository of JavaScript bestpractices with examples (WORK IN PROGRESS). @TODO: Cleanup and reorder  1. Avoid global functions or variables It is easy to forget how/where these are/were instantiated…….

This coding style makes semicolons omission no longer an option.

Also, new Function can be used for example as an alternative to eval if you want to emulate Function.prototype.apply in ie5.