Is it Necessary to use Strict Mode for JavaScript ?

Just Curious about using “Use Strict” mode in javascript
because the Famous Script Playtube did not use Strict Mode in their script

I am also working on the Script like Playtube so I just want to know that if they didn’t use Strict Mode so Can I also submit my script without using Strict Mode?

It’s Envato requirement and you should comply to the guideline to get your scripts accepted. So remember to add “use strict;” to every scripts that you wrote.