Patterns

A pattern is a sequence of text and placeholders to be formatted as a unit. Unless there is an error, the result of formatting a message is always the result of formatting a single pattern: either the single pattern that makes up a simple message, or the pattern of the matching variant in a complex message.

Almost anything not beginning with a . or a {{ is an unquoted pattern in MessageFormat. An unquoted pattern, on its own, is a simple message.

This is a pattern. It can include expressions like {$v} and {#b}markup{/b}.

{"v": "this"}

There are certain characters that can't appear in an unquoted pattern. You probably won't run into these at first.

Quoted Patterns Jump to heading#

A quoted pattern is a pattern that is enclosed in double braces ({{...}}). Quoting may be necessary because a pattern may contain characters that have a special meaning in the MessageFormat syntax, and the quotes make it clear that these characters should be interpreted literally.

Also, all patterns that appear in complex messages must be quoted. So in a message that has declarations:

.local $y = {1}
{{This pattern must be quoted.}}

Patterns in a matcher must also be quoted. We'll talk about matchers later.

Text Jump to heading#

Text is the translatable content of a pattern. Any Unicode code point is allowed, except for surrogate code points U+D800 through U+DFFF inclusive. The characters \, {, and } must be escaped.

Note that whitespace in text, including tabs, spaces, and newlines is significant and will be preserved during formatting.

.input {$num :number}
{{   This is the {$num} pattern   }}

{"num": 5}

An example with escaped characters:

Backslash: \\, left curly brace \{, right curly brace \}