Why is it already a window property?

Question

Why is foo a property of window when it's not used or initialized until a few lines later

for(var propName in window) {
    if(propName == 'foo') { //obv defined if its here
        console.log('WTF? Its already a part of window!!');
    }
}
console.log(typeof foo);
var foo = 'bar';

See http://stackoverflow.com/questions/7506844/javascript-function-scoping-and-hoisting — John Hascall, Mar 04 '16 at 18:54

score 1 · Answer 1 · edited Mar 04 '16 at 19:51

1

Your code actually look like this one due to var top hoisting.

When you declared the variable globally it is part of this object implicilty. So,your foo variable is part of window object which is refered by this object.

var foo;
for (var propName in window) {
    if (propName == 'foo') { //obv defined if its here
        console.log('WTF? Its already a part of window!!');
    }
}

console.log(typeof foo);
foo = 'bar';

this===window //true in this case

edited Mar 04 '16 at 19:51

Benjamin Albert

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answered Mar 04 '16 at 18:54

RIYAJ KHAN

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Thanks so much, had been trying figure this out for like hours. Knew it had to have a name. – bacon_is_good Mar 04 '16 at 19:12

Why is it already a window property?

1 Answers1