javascript - var x = x || "default val" not getting set properly if x is defined above it -

javascript - var x = x || "default val" not getting set properly if x is defined above it -

html:

<script type="text/javascript"> var x = "overriden"; </script> <script src="myjs.js"></script>

myjs.js:

$(document).ready(function(){ var x = x || "default val"; alert(x); // alerts "default val" , not "overriden" });

for reason, x ending "default val" , not "overriden", tho i'm setting "overriden" before include script reference myjs.js.

any thought why happening? i'm trying enable hosting page set override variable that's used in included js file, otherwise utilize default val.

what have after variable declaration hoisting applied:

var x; x = 5; $(document).ready(function(){ var x; x = x || "default"; });

it looks @ closest x , sees it's value undefined falsy value, x gets set "default". fine if in same scope, because declarations hoisted above assignments so:

var x = 5; var x = x || "default";

is just

var x; x = 5; x = x || "default";

this suggested pointless:

$(document).ready(function(){ x = x || "default"; });

it throw referenceerror if x not defined. either check in same scope or like:

$(document).ready(function(){ var x = window.x || "default"; });

invalid property reads don't cause referenceerror homecoming undefined instead.

javascript jquery