1360102 - About the global property with "var" in MDN.

Status: RESOLVED WONTFIX

(Developer Documentation Graveyard :: JavaScript, enhancement, P5)

Description

[WhiskyWosky]

:: Developer Documentation Request

      Request Type: Correction
     Gecko Version: unspecified
 Technical Contact: 

:: Details

Hi, MDN team,

According to MDN's article about introducing the "variable statement".
The paragraph before first sample code says:

"1. Declared variables are constrained in the execution context in which they are declared. Undeclared variables are always global."

But accrording to my tests,
I think that's not quite right,
The fact might is, 
No matter using var or let,
the undeclared varaibles would be a global variable until it hoisting to the scope where is a declared & same name variable exsist.
So, it's restrictive global, not totally global.

Please check the code below:

var x = 0; // replaced by x in t1.
var y = 0; // no replacement happened.
var z = 0; // replaced by z in t3.

(function t1() {

    x = 1; // undeclared, would go upward and fiding declared & same name variable.
    var y = 1; // replaced by y in t2.
    var w = 1; // replaced by w in t3.

    (function t2() {

        var x = 2; // it's local var, wouldn't, go upwrad.
        y = 2; // undeclared, would go upward.

        (function t3(){

            var x = 3; // it's local var, wouldn't, go upwrad.
            z = 3; // undeclared, would go upward.
            w = 3; // undeclared, would go upward.

        }());

        document.write("========= t2 ======<br/>");
        document.write("x: " + x + "<br/>"); // 2
        document.write("y: " + y + "<br/>"); // 2
        document.write("z: " + z + "<br/>"); // 3
        document.write("w: " + w + "<br/>"); // 3

    }());

    document.write("========= t1 ======<br/>");
    document.write("x: " + x + "<br/>"); // 1
    document.write("y: " + y + "<br/>"); // 2
    document.write("z: " + z + "<br/>"); // 3
    document.write("w: " + w + "<br/>"); // 3

}());

document.write("========= global ======<br/>");
document.write("x: " + x + "<br/>"); // 1
document.write("y: " + y + "<br/>"); // 0
document.write("z: " + z + "<br/>"); // 3
document.write("w: " + w + "<br/>"); // w would be "not defined", because it's undeclared in global scope.

So, please correct me if I misunderstood anything.
Thanks a lot.
Wish you guys have a good day. ^^

Comment 1

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