What anti-patterns exist for JavaScript? [closed]

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Language:

  • Namespace polluting by creating a large footprint of variables in the global context.

  • Binding event handlers in the form ‘foo.onclick = myFunc’ (inextensible, should be using attachEvent/addEventListener).

  • Using eval in almost any non-JSON context

  • Almost every use of document.write (use the DOM methods like document.createElement)

  • Prototyping against the Object object (BOOM!)

  • A small one this, but doing large numbers of string concats with ‘+’ (creating an array and joining it is much more efficient)

  • Referring to the non-existent undefined constant

Design/Deployment:

  • (Generally) not providing noscript support.

  • Not packaging your code into a single resource

  • Putting inline (i.e. body) scripts near the top of the body (they block loading)

Ajax specific:

  • not indicating the start, end, or error of a request to the user

  • polling

  • passing and parsing XML instead of JSON or HTML (where appropriate)

Many of these were sourced from the book Learning JavaScript Design by Addy Osmati: https://www.oreilly.com/library/view/learning-javascript-design/9781449334840/ch06.html

edit: I keep thinking of more!

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