There’s an old saying in Special Forces, “Slow is smooth. Smooth is fast.” Or to put it the way we learned as children, “haste makes waste”.
I would say slow down a little. And every coder makes mistakes. But as you get better, you make fewer of them and you get better at finding them.
Do you use a linter? That might catch a few things. As far as speling mistakes (I make a lot), I use an extension Code Spell Checker on VSC - it flags little mistakes.
But I’d recommend learning to code slowly and smoothly. Check and debug as you go. As you get better, you can speed up a bit and stretch out the space between testing, but go slow at first. Focus on accuracy and planning in the beginning.
Debugging takes at least 10x time comparing to coding, so if you take a good moment to think and then code “slowly and smoothly” as @kevinSmith suggested that would be your top speed. Typing fast will not make you code fast, saving snippets will
Markup validation is an important step towards ensuring the technical quality of web pages. However, it is not a complete measure of web standards conformance.
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Mark-up validators cannot see the “big picture” on a web page,[5][6] but they excel at picking up missed closing tags and other technicalities.
A linter is just a program that checks that your code is formatted correctly and sometimes catches problems. They drive you crazy until you get used to them. Most editors should be able to set them up. For JS, eslint is very common and the Air B&B settings are probably the most common.