The JavaScript exception "rest parameter may not have a default" occurs when a rest parameter has a default value. Because the rest parameter always creates an array, the default value would never apply.

Panic support in the standard library.

The JavaScript exception "cannot use ?? unparenthesized within || and && expressions" occurs when an nullish coalescing operator is used with a logical OR or logical AND in the same expression without parentheses.

The keyPoints attribute indicates the simple duration of an animation.

The JavaScript exception "super() is only valid in derived class constructors" occurs when the super() call is used somewhere that's not the body of a constructor in a class with extends keyword.

`dyn` is a prefix of a trait object’s type.

The JavaScript exception "repeat count must be less than infinity" occurs when the String.prototype.repeat() method is used with a count argument that is infinity.

The JavaScript exception "can't access lexical declaration 'X' before initialization" occurs when a lexical variable was accessed before it was initialized. This happens within any scope (global, module, function, or block) when let or const variables are accessed before the place where they are declared is executed.

Organize code into modules.

The JavaScript exception "negated character class with strings in regular expression" occurs when a v-mode character class is negated and may be able to match a string (more than one character).