The JavaScript exception "illegal character" occurs when the lexer reads a character that's not part of a string literal, and the character cannot constitute a valid token in the language.

The JavaScript warning "unreachable code after return statement" occurs when using an expression after a return statement, or when using a semicolon-less return statement but including an expression directly after.

The v-mathematical attribute indicates the alignment coordinate for glyphs to achieve mathematical baseline alignment for vertically oriented glyph layouts. The value is an offset in the font coordinate system relative to the glyph-specific vert-origin-x attribute.

The JavaScript strict mode-only exception "0-prefixed octal literals are deprecated; use the "0o" prefix instead" occurs when deprecated octal literals (0 followed by digits) are used.

An iterator that splits an environment variable into paths according to platform-specific conventions.

The crossorigin attribute, valid on the <image> and <feImage> elements, provides support for configuration of the Cross-Origin Resource Sharing (CORS) requests for the element's fetched data.

The JavaScript exception "missing ) after argument list" occurs when there is an error with how a function is called. This might be a typo, a missing operator, or an unescaped string.

A lazy iterator producing elements in the symmetric difference of `HashSet`s.

An iterator over the entries of a `HashMap`.

The Temporal.PlainYearMonth object represents the year and month of a calendar date, without a day or time zone; for example, an event on a calendar that happens during the whole month. It is fundamentally represented as an ISO 8601 calendar date, with year, month, and day fields, and an associated calendar system. The day is used to disambiguate the year-month in non-ISO calendar systems.