javascript - Can't access the window level variable even though it exists. returns undefined when accessed -

i trying access window level variable in script in window.onload(), returns undefined. when console log or try type in window in debug console, shows me variable exists on window object , has value. unclear why happening , there way access it? please correct me if doing wrong , point me in right direction. appreciated.

update: window._vp variable declared in script of live website , trying access particular variable using chrome extension.

my script:

window.onload = _ => {     console.log("window._vp is:", window._vp); } 

website script:

var _vp = {}; _vp['isdashavailable'] = false; //... 

you can see behavior in following screenshot of dev tool console:

thank you.

i believe issue extensions isolated context, detailed in so post context isolation faced identical issue.

you should try following method quoted other answer:

method 2b: using function

for big chunk of code, quoting string not feasible. instead of using array, function can used, , stringified:

var actualcode = '(' + function() {     // code executed in local scope.     // example, following not overwrite global `alert` method     var alert = null;     // overwrite global variable, prefix `window`:     window.alert = null; } + ')();';  var script = document.createelement('script'); script.textcontent = actualcode; (document.head||document.documentelement).appendchild(script); script.remove(); 

this method works, because + operator on strings , function converts objects string. if intend on using code more once, it's wise create function avoid code repetition. implementation might like:

function injectscript(func) {     var actualcode = '(' + func + ')();'     ... } injectscript(function() {    alert("injected script"); }); 

note: since function serialized, original scope, , bound properties lost!

var scripttoinject = function() {     console.log(typeof scripttoinject); }; injectscript(scripttoinject); // console output:  "undefined"