Question

Yesterday I found this function:

function clone(obj) {     return typeof obj === 'undefined' ?         this : (clone.prototype = Object(obj), new clone); } 

I though that i saw alot in Javascript, but this syntax is unknown for me:

 clone.prototype = Object(obj), new clone 

Can someone explain me how to read this?? Can you give me link to proper definition ? I couldn’t find it in Mozilla’s MDC, and dont know how to find this on web, but this is first time ever I saw that syntax. Thanks for effort here.

Final solution:

I did some testing according to answers here and there is what I found:

var b; b=alert('test'),6; alert(b);  // alert undefined b=5,alert('test2'); alert(b);  // alert 5 

Thanks to christoph research we found more:

var a, b, c; a = 1, 2;   // a is 1 (b = 1), 2; // b is 1 - same as above! c = (1, 2); // c is 2 

Ahh and I tested it also on IE6 and it works, so this have to be realy old syntax and there is no information about it? 🙁 Strange…

Both of you guys gave good solution, thanks for solution here!

Answer 1

Your ‘final solution’ gives unexpected results because of operator precedence. The following example might help to clarify the issue:

var a, b, c; a = 1, 2;   // a is 1 (b = 1), 2; // b is 1 - same as above! c = (1, 2); // c is 2 

Also notice that

var a = 1, 2; 

produces a syntax error!