JSON5 (https://spec.json5.org)
https://github.com/json5/json5
nodejs讀取設定檔常使用json格式(http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf, https://tools.ietf.org/html/rfc8259)， 但是json在描述時限制較多，例如在key要雙引號，字串要用雙引號不能用單引號，不能有註解等。
因此可讀性變差，JSON5主要將ECMAScript 5.1語法引入，整體看來，syntax對於熟悉javascript的使用者更友善
幾個比較大的差異
- key不一定需要引號(根據ECMAScript 5.1 IdentifierName規則)
- Objects may have a single trailing comma.
- Arrays may have a single trailing comma.
- Strings may be single quoted/支援多行/支援 \x的escape (U+0000 through U+00FF)
- String更寬容的escape字元包含
- JSON:All Unicode characters may be placed within the
quotation marks, except for the characters that MUST be escaped: quotation mark, reverse solidus, and the control characters (U+0000 through U+001F). - JSON5:All Unicode characters may be placed within the quotation marks, except for the characters that must be escaped: the quotation mark used to begin and end the string, reverse solidus, and line terminators.
- JSON:All Unicode characters may be placed within the
- Number支援更廣泛的表示方式(eg. hex, + sign), inf, NaN
- Single and multi-line comments are allowed
- 更寬容的whitespace支援 (JSON只支援0x20, 0x09, 0x0A, 0x0D)