Declaring a variable without var in function

Question

I tried to the opposite of what the exercise wanted. Instead of declaring a variable with var inside the function, I did it like this:

function myLocalScope() {
  'use strict';

  // Only change code below this line
  myVar = "bebe"
  console.log('inside myLocalScope', myVar);
}
myLocalScope();

// Run and check the console
// myVar is not defined outside of myLocalScope
console.log('outside myLocalScope', myVar);

I thought that since I used no var it would be global now. But it just says its not defined. Not even in the local scope. If I add var inside the function, then the function works.

Does this answer your question? [What does "use strict" do in JavaScript, and what is the reasoning behind it?](https://stackoverflow.com/questions/1335851/what-does-use-strict-do-in-javascript-and-what-is-the-reasoning-behind-it) — John Montgomery, Aug 19 '20 at 23:07

score 1 · Answer 1 · answered Aug 18 '20 at 07:51

Remove "use strict" and it should work . With strict mode, you can not use undeclared variables.

function myLocalScope() {
 
  // Only change code below this line
  myVar = "bebe"
  console.log('inside myLocalScope', myVar);
}
myLocalScope();

// Run and check the console
// myVar is not defined outside of myLocalScope
console.log('outside myLocalScope', myVar);

Radical Edward · Accepted Answer · 2020-08-18T07:58:27.217

Yes: Variable wont be accessible outside of function if you are using use strict unless you assign it global scope, in this case you have to either remove use strict or prefix your variables with window. like so: window.myVar . As window is global, your variable will be available outside too.

function myLocalScope() {
  'use strict';

  // Only change code below this line
  window.myVar = "bebe"
  console.log('inside myLocalScope', myVar);
}
myLocalScope();

// Run and check the console
// myVar is not defined outside of myLocalScope
console.log('outside myLocalScope', window.myVar);

Declaring a variable without var in function

2 Answers2