ReferenceError and the global object

by

Because with window.foo you are explicitly looking for foo property of window object which is not the case in latter option. In the latter option, if foo isn’t defined, you should as developer be able to know that it isn’t defined and get the clear error warning rather than interpreter setting it to undefined on its own (like first case) which will lead to unexpected results.

Reference Error:

Represents an error when a non-existent variable is referenced.
A ReferenceError is thrown when trying to dereference a variable that has not been declared.

Take a look at this article for more info:

Quoting from above article:

A Reference is considered unresolvable if its base value is undefined. Therefore a property reference is unresolvable if the value before the dot is undefined. The following example would throw a ReferenceError but it doesn’t because TypeError gets there first. This is because the base value of a property is subject to CheckObjectCoercible (ECMA 5 9.10 via 11.2.1) which throws a TypeError when trying to convert Undefined type to an Object.

Examples:

var foo;
foo.bar; //TypeError (base value, foo, is undefined)
bar.baz; //ReferenceError (bar is unersolvable)
undefined.foo; //TypeError (base value is undefined)

References which are neither properties or variables are by definition unresolvable and will throw a ReferenceError, So:

foo; //ReferenceError

More Related Contents:

  1. Have a pop up window when clicking on an image
  2. Uncaught ReferenceError: $ is not defined?
  3. Is there a way to detect if a browser window is not currently active?
  4. JavaScript, browsers, window close – send an AJAX request or run a script on window closing
  5. window.location.href and window.open () methods in JavaScript
  6. What’s the difference between window.location= and window.location.replace()?
  7. How to prevent closing browser window?
  8. Javascript window.open pass values using POST
  9. JavaScript – Get Browser Height
  10. $(window).scrollTop() vs. $(document).scrollTop()
  11. window.open() on a multi-monitor/dual-monitor system – where does window pop up?
  12. What’s the difference between self and window?
  13. Is it possible to create desktop applications with node.js? [duplicate]
  14. location.host vs location.hostname and cross-browser compatibility?
  15. Difference between screen.availHeight and window.height()
  16. window.open popup getting blocked during click event
  17. javascript – document.write error?
  18. jQuery/JS, iOS 4 and $(document).height() problems
  19. Storing a variable in the JavaScript ‘window’ object is a proper way to use that object?
  20. javascript to get paragraph of selected text in web page
  21. JavaScript window.open only if the window does not already exist
  22. When to use window.opener / window.parent / window.top
  23. How to run function of parent window when child window closes?
  24. js window.open then print()
  25. onClick Function “this” Returns Window Object
  26. Disabling enter key for form
  27. Clear localStorage on tab/browser close but not on refresh
  28. Could a website force the browser to go into fullscreen mode?
  29. How to get a dom element in a new window?
  30. What are window.opener / window.parent / window.top?

Leave a Comment