v1.0.0 [<a href="https://github.com/json5/json5/tree/v1.0.0">code</a>, <a href="https://github.com/json5/json5/compare/v0.5.1...v1.0.0">diff</a>]

This release includes major internal changes and public API enhancements.

Major JSON5 officially supports Node.js v4 and later. Support for Node.js v0.10 and v0.12 have been dropped.
New: Unicode property names and Unicode escapes in property names are supported. (#1)
New: stringify outputs trailing commas in objects and arrays when a space option is provided. (#66)
New: JSON5 allows line and paragraph separator characters (U+2028 and U+2029) in strings in order to be compatible with JSON. However, ES5 does not allow these characters in strings, so JSON5 gives a warning when they are parsed and escapes them when they are stringified. (#70)
New: stringify accepts an options object as its second argument. The supported options are replacer, space, and a new quote option that specifies the quote character used in strings. (#71)
New: The CLI supports STDIN and STDOUT and adds --out-file, --space, and --validate options. See json5 --help for more information. (#72, #84, and #108)
New: In addition to the white space characters space \t, \v, \f, \n, \r, and \xA0, the additional white space characters \u2028, \u2029, and all other characters in the Space Separator Unicode category are allowed.
New: In addition to the character escapes ‘’,",\`, \b, \f, \n, \r, and \t, the additional character escapes \v and \0, hexadecimal escapes like \x0F, and unnecessary escapes like \a are allowed in string values and string property names.
New: stringify outputs strings with single quotes by default but intelligently uses double quotes if there are more single quotes than double quotes inside the string. (i.e. ‘stringify('Stay here.’)outputs 'Stay here.'whilestringify('Let\'s go.')outputs"Let's go."`)
New: When a character is not allowed in a string, stringify outputs a character escape like \t when available, a hexadecimal escape like \x0F when the Unicode code point is less than 256, or a Unicode character escape like \u01FF, in that order.
New: stringify checks for a toJSON5 method on objects and, if it exists, stringifies its return value instead of the object. toJSON5 overrides toJSON if they both exist.
New: To require or import JSON5 files, use ‘require('json5/lib/register’) orimport 'json5/lib/register'. Previous versions usedjson5/lib/require`, which still exists for backward compatibility but is deprecated and will give a warning.
New: To use JSON5 in browsers, use the file at dist/index.js or https://unpkg.com/json5@^1.0.0.
Fix: stringify properly outputs Infinity and NaN. (#67)
Fix: isWord no longer becomes a property of JSON5 after calling stringify. (#68 and #89)
Fix: stringify no longer throws when an object does not have a prototype. (#154)
Fix: stringify properly handles the key argument of toJSON(key) methods. toJSON5(key) follows this pattern.
Fix: stringify accepts Number and String objects as its space argument.
Fix: In addition to a function, stringify also accepts an array of keys to include in the output as its replacer argument. Numbers, Number objects, and String objects will be converted to a string if they are given as array values.

v0.5.1 [<a href="https://github.com/json5/json5/tree/v0.5.1">code</a>, <a href="https://github.com/json5/json5/compare/v0.5.0...v0.5.1">diff</a>]

This release includes a minor fix for indentations when stringifying empty arrays.

Fix: Indents no longer appear in empty arrays when stringified. (#134)

v0.5.0 [<a href="https://github.com/json5/json5/tree/v0.5.0">code</a>, <a href="https://github.com/json5/json5/compare/v0.4.0...v0.5.0">diff</a>]

This release includes major internal changes and public API enhancements.

Major: JSON5 officially supports Node.js v4 LTS and v5. Support for Node.js v0.6 and v0.8 have been dropped, while support for v0.10 and v0.12 remain.
Fix: YUI Compressor no longer fails when compressing json5.js. (#97)
New: parse and the CLI provide line and column numbers when displaying error messages. (#101; awesome work by @amb26.)

v0.4.0 [<a href="https://github.com/json5/json5/tree/v0.4.0">code</a>, <a href="https://github.com/json5/json5/compare/v0.2.0...v0.4.0">diff</a>]

Note that v0.3.0 was tagged, but never published to npm, so this v0.4.0 changelog entry includes v0.3.0 features.

This is a massive release that adds stringify support, among other things.

Major: JSON5.stringify() now exists! This method is analogous to the native JSON.stringify(); it just avoids quoting keys where possible. See the usage documentation for more. (#32; huge thanks and props @aeisenberg!)
New: NaN and -NaN are now allowed number literals. (#30; thanks @rowanhill.)
New: Duplicate object keys are now allowed; the last value is used. This is the same behavior as JSON. (#57; thanks @jordanbtucker.)
Fix: Properly handle various whitespace and newline cases now. E.g. JSON5 now properly supports escaped CR and CRLF newlines in strings, and JSON5 now accepts the same whitespace as JSON (stricter than ES5). (#58, #60, and #63; thanks @jordanbtucker.)
New: Negative hexadecimal numbers (e.g. -0xC8) are allowed again. (They were disallowed in v0.2.0; see below.) It turns out they are valid in ES5, so JSON5 supports them now too. (#36; thanks @jordanbtucker!)

v0.2.0 [<a href="https://github.com/json5/json5/tree/v0.2.0">code</a>, <a href="https://github.com/json5/json5/compare/v0.1.0...v0.2.0">diff</a>]

This release fixes some bugs and adds some more utility features to help you express data more easily:

Breaking: Negative hexadecimal numbers (e.g. -0xC8) are rejected now. While V8 (e.g. Chrome and Node) supported them, it turns out they're invalid in ES5. This has been fixed in V8 (and by extension, Chrome and Node), so JSON5 officially rejects them now, too. (#36)
New: Trailing decimal points in decimal numbers are allowed again. (They were disallowed in v0.1.0; see below.) They're allowed by ES5, and differentiating between integers and floats may make sense on some platforms. (#16; thanks @Midar.)
New: Infinity and -Infinity are now allowed number literals. (#30; thanks @pepkin88.)
New: Plus signs (+) in front of numbers are now allowed, since it can be helpful in some contexts to explicitly mark numbers as positive. (E.g. when a property represents changes or deltas.)
Fix: unescaped newlines in strings are rejected now. (#24; thanks @Midar.)

v0.1.0 [<a href="https://github.com/json5/json5/tree/v0.1.0">code</a>, <a href="https://github.com/json5/json5/compare/v0.0.1...v0.1.0">diff</a>]

This release tightens JSON5 support and adds helpful utility features:

New: Support hexadecimal numbers. (Thanks @MaxNanasy.)
Fix: Reject octal numbers properly now. Previously, they were accepted but improperly parsed as base-10 numbers. (Thanks @MaxNanasy.)
Breaking: Reject "noctal" numbers now (base-10 numbers that begin with a leading zero). These are disallowed by both JSON5 and JSON, as well as by ES5's strict mode. (Thanks @MaxNanasy.)
New: Support leading decimal points in decimal numbers. (Thanks @MaxNanasy.)
Breaking: Reject trailing decimal points in decimal numbers now. These are disallowed by both JSON5 and JSON. (Thanks @MaxNanasy.)
Breaking: Reject omitted elements in arrays now. These are disallowed by both JSON5 and JSON.
Fix: Throw proper SyntaxError instances on errors now.
New: Add Node.js require() hook. Register via json5/lib/require.
New: Add Node.js json5 executable to compile JSON5 files to JSON.

v0.0.1 [<a href="https://github.com/json5/json5/tree/v0.0.1">code</a>, <a href="https://github.com/json5/json5/compare/v0.0.0...v0.0.1">diff</a>]

This was the first implementation of this JSON5 parser.

Support unquoted object keys, including reserved words. Unicode characters and escape sequences sequences aren't yet supported.
Support single-quoted strings.
Support multi-line strings.
Support trailing commas in arrays and objects.
Support comments, both inline and block.

v0.0.0 [<a href="https://github.com/json5/json5/tree/v0.0.0">code</a>]

Let's consider this to be Douglas Crockford's original json_parse.js — a parser for the regular JSON format.