How does variable assignment work in JavaScript?

by

In the first example, you are setting a property of an existing object. In the second example, you are assigning a brand new object.

a = b = {};

a and b are now pointers to the same object. So when you do:

a.foo = 'bar';

It sets b.foo as well since a and b point to the same object.

However!

If you do this instead:

a="bar";

you are saying that a points to a different object now. This has no effect on what a pointed to before.

In JavaScript, assigning a variable and assigning a property are 2 different operations. It’s best to think of variables as pointers to objects, and when you assign directly to a variable, you are not modifying any objects, merely repointing your variable to a different object.

But assigning a property, like a.foo, will modify the object that a points to. This, of course, also modifies all other references that point to this object simply because they all point to the same object.

More Related Contents:

  1. Twitter Bootstrap Tabs: Go to Specific Tab on Page Reload or Hyperlink
  2. How do I render a Word document (.doc, .docx) in the browser using JavaScript?
  3. How do I chain three asynchronous calls using jQuery promises?
  4. How can I let a table’s body scroll but keep its head fixed in place?
  5. Set default value of Javascript object attributes
  6. Javascript – telling setInterval to only fire x amount of times?
  7. Angular 2 router event listener
  8. how to countdown to a date
  9. How to open a file / browse dialog using javascript?
  10. CSS media queries and jQuery window .width() do not match
  11. Firebase TIMESTAMP to date and Time
  12. Rotate image with javascript
  13. Responsive horizontal page sliding
  14. Get the first integers in a string with JavaScript
  15. Validate phone number using javascript
  16. Running V8 Javascript Engine Standalone
  17. Angular ui router unit testing (states to urls)
  18. How can I mock dependencies for unit testing in RequireJS?
  19. how to resolve iframe cross domain issue [duplicate]
  20. Putting default value in
  21. Checking if a message was sent from a DM channel type not working
  22. Transpile Async Await proposal with Babel.js?
  23. How can I stop jQuery.ajax() from logging failures to the console?
  24. Calculate Time Difference with JavaScript
  25. let user scrolling stop jquery animation of scrolltop?
  26. Google Maps API without key?
  27. Javascript – regex – word boundary (\b) issue
  28. Hot to get incomplete datetime-local input values
  29. Add timestamp to named column in Google Spreadsheet onEdit script
  30. ES6 – declare a prototype method on a class with an import statement

Leave a Comment