Question 1

What's the difference between encodeURI and encodeURIComponent?

Accepted Answer

encodeURI preserves a whole URL and leaves separators like :/?&= alone. encodeURIComponent encodes a single piece and escapes separators too. For a parameter value you need the latter — otherwise an & inside your value starts a new parameter.

Question 2

Why is a space sometimes + and sometimes %20?

Accepted Answer

In form submissions (application/x-www-form-urlencoded) a space becomes +; in a URL path it must be %20. Using the wrong one leaves a literal plus sign inside your value.

URL Encode / Decode