foo in bar - 'in' operator javascript?

Question

I recently read a tutorial on CSS browser feature detection... The end product was something like this...

var prefix = [\'Moz\', \'webkit\', \'O\', \'ms\', \'Kht         


        

Answer 1

The statement if (foo in bar) tests whether the object bar has a property named foo. It doesn't test for a property with the value foo.

That is:

var bar = {"a" : "x", "b" : "y"};
alert("a" in bar); // true
alert("x" in bar); // false

You can use this syntax on arrays because they are a type of object. If bar is an array then foo in bar will be true if foo is either a numeric index of the array that has a value or if foo is some other property or method name.

Also, if this is used to check values in an array HOW is test_style = document.createElement('div').style an array?

test_style is an object, not an array.