What is the difference between "for ... in" and "for each ... in" in javascript?

Question

I know that in C # you use foreach as follows: foreach string str in array1 {console.writeline(str);} Is "for everyone ... in" the same as in JavaScript?

Answer 1

Afaik only Firefox supports for each...in. It is not part of any standard, and most tools like JSLint will cause errors if they encounter it.

The difference is that it for...incrosses the keysobject, while it for each...inperforms cyclic checks.

- for each

for (var key in obj) {
    console.log(obj[key]);
}

.

: , #. : for...in ( ):

, . for...in , , (, "foo" Array.prototype), for...in .

for:

for(var i = 0, l = arr.length; i<l; i++)

:

for(var i = arr.length; i--;)

Answer 2

JavaScript for each in. , .

for..in JavaScript , , - . for..in , for each #. , , . ( , - , .) for each . .

Answer 3

" ... " , ... . :

http://www.dustindiaz.com/for-each-in/

Answer 4

in (, ) javascript object - javascript ( Object).

var obj = {
    a: "aaa",
    b: "bbb"
};

for (var key in obj) {
    if (obj.hasOwnProperty(key)){
        console.log("obj has a property " + key + ", with a value of " + obj[key]);
    }
}

in , , hasOwnProperty, , , .

, in , , for/while, .