Javascript Weird construction in simple object?

Question

Pretty simple code :

var t = new function () //line 1
    {
        this.a1 = function () {

            return function () {
                alert("1");
            };
        }();
        this.a2 = function () {
            alert("a2");
        };

    }; //line 16
t.a1();

But jsBin red line bellow tells me :

Line 1: var t = new function () --- Weird construction. Delete 'new'.

Line 16: }; --- Missing '()' invoking a constructor.

the code is working fine.

What am I doing wrong ?

Working fine in my Firefox/Chrome. Which browser are you running trouble into? — Abdul Munim, Dec 10 '11 at 09:34
@Munim jsBin red line bellow .....Ive edited. look at the link . thanks. — Royi Namir, Dec 10 '11 at 09:35
See this question: http://stackoverflow.com/questions/2274695/new-function-with-lower-case-f-in-javascript — Hristo, Dec 10 '11 at 09:42
@Hristo How the hell did you find this ??? :) thanks I will look at that. — Royi Namir, Dec 10 '11 at 09:42
@RoyiNamir Your code is correct. However jsbin uses jslint. And jslint says "this code is silly". Thus it flags a warning. I recommend you don't use `new function () { }` because there are better alternatives. — Raynos, Dec 10 '11 at 09:45
@Hristo Still I cant understand why my code is BAd..... I've read the link answer , and the solution was to create an inside instance in autoexecute the wrapper function... thats fine also.. but I want to know why my code is bad — Royi Namir, Dec 10 '11 at 09:46
@Royi... I found it by doing a simple Google search. Here's another one http://stackoverflow.com/questions/6440193/constructing-object-with-new-function-vs-invoking-function-with-function... but I can't exactly tell you why its bad. I'm not saying it is bad or good, it just seems that `new function() {}` is not common practice. Plus, if jsBin uses jsLint and jsLint was written by Douglas Crockford and it tells you to not do that, then I would listen because Douglas Crockford is the JavaScript guru. — Hristo, Dec 10 '11 at 09:58

score 2 · Accepted Answer · answered Dec 10 '11 at 09:39

2

If you're going to write an "anonymous type" equivalent to:

var _anonymous_type = function () {
    ...
}

var t = new _anonymous_type();

You should:

var t = new (function () {
    ...
})();

See the difference from you code? :)

answered Dec 10 '11 at 09:39

Jeffrey Zhao

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The second is just an inlining of the first ... why would that be considered wrong? – ripper234 Mar 19 '12 at 14:11
@Jeffrey Zhao I got the same warning with your new suggesting (no pun intended) – Sapphire_Brick Dec 30 '19 at 02:59

score 1 · Answer 2 · answered Dec 10 '11 at 09:37

1

Try this:

var t = function () //line 1
    {
        this.a1 = function () {

            return function () {
                alert("1");
            };
        }();
        this.a2 = function () {
            alert("a2");
        };

    }; //line 16

var x = new t();
x.a1();

answered Dec 10 '11 at 09:37

regality

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I can do that ALSO.... But my Code is syntactical fine. I can't see any reason why it wont work.... – Royi Namir Dec 10 '11 at 09:39
Technically there is nothing wrong with `var t = new function()...`, but there isn't a good reason to do that. Hence the *weird* constructor. – regality Dec 10 '11 at 09:53

Javascript Weird construction in simple object?

2 Answers2