The xlink:href attribute defines a reference to a resource as a reference IRI. The exact meaning of that link depends on the context of each element using it.

The xlink:title attribute is used to describe the meaning of a link or resource in a human-readable fashion.

Trailing commas (sometimes called "final commas") can be useful when adding new elements, parameters, or properties to JavaScript code. If you want to add a new property, you can add a new line without modifying the previously last line if that line already uses a trailing comma. This makes version-control diffs cleaner and editing code might be less troublesome.

# Contributors by commit history https://github.com/mdn/content/commits/main/files/en-us/web/javascript/index.md # Original Wiki contributors Arpitgoyalgg chrisdavidmills m.karimcu aajinformation h...

The JavaScript strict mode-only exception "Assignment to undeclared variable" occurs when the value has been assigned to an undeclared variable.

The JavaScript exception "raw bracket is not allowed in regular expression with unicode flag" occurs when a Unicode-aware regular expression pattern contains a raw bracket ({, }, ]) that is not part of a quantifier or character class.

The JavaScript exception "can't define property "x": "obj" is not extensible" occurs when Object.preventExtensions() marked an object as no longer extensible, so that it will never have properties beyond the ones it had at the time it was marked as non-extensible.

The JavaScript exception "duplicate formal argument x" or "duplicate argument names not allowed in this context" occurs when a function creates two or more parameter bindings with the same name, and the function is not a non-strict function with only simple parameters.

The JavaScript exception "is not a non-null object" occurs when an object is expected somewhere and wasn't provided. null is not an object and won't work.

The JavaScript exception "invalid regular expression flag" occurs when the flags in a regular expression contain any flag that is not one of: d, g, i, m, s, u, v, or y. It may also be raised if the expression contains more than one instance of a valid flag, or when the u and v flags are used together.