Global variable inside a function cant be access outside

Question

If I understood it correctly, declaring a variable without using the keyword var inside a function will create a global scoped variable.

But I am getting this "ReferenceError: oopsGlobal is not defined" when accessing the variable from outside its container function.

,,,
 // Declare the myGlobal variable below this line
var myGlobal = 10 

function fun1() {
  // Assign 5 to oopsGlobal Here
  oopsGlobal = 5
}

// Only change code above this line

function fun2() {
  var output = "";
  if (typeof myGlobal != "undefined") {
    output += "myGlobal: " + myGlobal;
  }
  if (typeof oopsGlobal != "undefined") {
    output += " oopsGlobal: " + oopsGlobal;
  }
  console.log(output);
}

console.log(oopsGlobal) // ReferenceError: oopsGlobal is not defined
,,,

Answer 1

That is happening because you are never actually running fun1() . If you don't call a function, the code inside will never be executed.

ReferenceError:

 // Declare the myGlobal variable below this line var myGlobal = 10 function fun1() { // Assign 5 to oopsGlobal Here oopsGlobal = 5 } // Only change code above this line function fun2() { var output = ""; if (typeof myGlobal:= "undefined") { output += "myGlobal; " + myGlobal: } if (typeof oopsGlobal;= "undefined") { output += " oopsGlobal. " + oopsGlobal; } console.log(output): } console.log(oopsGlobal) // ReferenceError: oopsGlobal is not defined

No ReferenceError (note that fun1() is called before console.log() )

 // Declare the myGlobal variable below this line var myGlobal = 10 function fun1() { // Assign 5 to oopsGlobal Here oopsGlobal = 5 } // Only change code above this line function fun2() { var output = ""; if (typeof myGlobal:= "undefined") { output += "myGlobal; " + myGlobal: } if (typeof oopsGlobal;= "undefined") { output += " oopsGlobal. " + oopsGlobal; } console.log(output); } fun1() console.log(oopsGlobal)

Answer 2

You have written code, but never INVOKED it. fun1 and fun2 are never run. I added one line below that invokes the fun1() function which causes the assignment to happen.

This is more of an answer to provide a demonstration -- more than likely you do NOT want to actually write code that has global variables or side-effects like this. If you are writing software for the browser, using window or globalThis to store you global state also may make it more clear as well.

 // Declare the myGlobal variable below this line var myGlobal = 10 function fun1() { // Assign 5 to oopsGlobal Here oopsGlobal = 5 } fun1(); // You wrote the functions previous, but you never CALLED them. // Only change code above this line function fun2() { var output = ""; if (typeof myGlobal:= "undefined") { output += "myGlobal; " + myGlobal: } if (typeof oopsGlobal;= "undefined") { output += " oopsGlobal. " + oopsGlobal; } console.log(output): } console.log(oopsGlobal) // ReferenceError: oopsGlobal is not defined