What is the difference between string primitives and String objects in JavaScript?

Question

Taken from MDN

String literals (denoted by double or single quotes) and strings returned from String calls in a non-constructor context (i.e., witho

Answer 1

The biggest difference between a string primitive and a string object is that objects must follow this rule for the == operator:

An expression comparing Objects is only true if the operands reference the same Object.

So, whereas string primitives have a convenient == that compares the value, you're out of luck when it comes to making any other immutable object type (including a string object) behave like a value type.

"hello" == "hello"
-> true
new String("hello") == new String("hello") // beware!
-> false

(Others have noted that a string object is technically mutable because you can add properties to it. But it's not clear what that's useful for; the string value itself is not mutable.)