[Webkit-unassigned] [Bug 201695] New: Function declaration statements in false conditional contexts create working functions and assign them to identifiers in the parent context.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=201695

            Bug ID: 201695
           Summary: Function declaration statements in false conditional
                    contexts create working functions and assign them to
                    identifiers in the parent context.
           Product: WebKit
           Version: Safari 12
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: dlivesay at mac.com

The following statement
    if (false) {
        function myFunction(){
            return "I work!";
        }
    }
should declare a variable, "myFunction," in the parent namespace, if it doesn't already exist, but it should neither assign a value to the variable nor create a function. This behavior is confirmed, for example, in the Google Chrome console:
 > if(false){function myFunction(){return "I work!";}}
 < undefined
 > "myFunction" in window
 < true
 > typeof myFunction
 < "undefined"
And attempting to invoke myFunction throws a TypeError error.

In the Safari console, however, a working function is created and assigned to the variable:
 > if(false){function myFunction(){return "I work!";}}
 < undefined
 > "myFunction" in window
 < true
 > typeof myFunction
 < "function"
 > myFunction()
 < "I work!"

The behavior is the same if the variable already exists and has a value in the parent namespace:
 > myFunction = "just a string"
 < "just a string"
 > typeof myFunction
 < "string"
 > if(false){function myFunction(){return "I work!";}}
 < undefined
 > typeof myFunction
 < "function"
Thus, the existing value is overwritten with the function.

-- 
You are receiving this mail because:
You are the assignee for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.webkit.org/pipermail/webkit-unassigned/attachments/20190911/7be381a9/attachment.html>