JAVASCRIPT Global Variable become undefined inside a setTimeout

Asked Mar 24 '17 at 16:26

Active Mar 24 '17 at 16:35

Viewed 626 times

Someone can explain me why this variable become "undefined" ?

var a=1;
var cond=false;
alert(a);

setTimeout(function(){ 

 alert(a); // <---------------- WHY IS UNDEFINED????
 alert(cond);
  if (cond==true) var a=2; // <------ IF I COMMENT THIS OR SET cond=false, WHY a IS UNDEFINED???
 alert(a);
}, 500);

Thanks.

asked Mar 24 '17 at 16:26

manmasel

Use window.a an it's work. – Happyriri Mar 24 '17 at 16:28
Hi Quentin, can you tell me the link of duplicate question? thanks. – manmasel Mar 24 '17 at 16:33
the link is in the banner: http://stackoverflow.com/questions/1162561/whats-wrong-with-defining-javascript-variables-within-if-blocks – Nelson Teixeira Mar 24 '17 at 16:34
1

This is also a dupe of [Surprised that global variable has undefined value in JavaScript](http://stackoverflow.com/q/9085839/4642212). – Sebastian Simon Mar 24 '17 at 16:34
Ok Thanks Nelson. – manmasel Mar 24 '17 at 16:35
Thanks also to Xufox. – manmasel Mar 24 '17 at 16:41

JAVASCRIPT Global Variable become undefined inside a setTimeout

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