Pretty

Pretty is a Go package that provides fast methods for formatting JSON for human readability, or to compact JSON for smaller payloads.

Getting Started

Installing

To start using Pretty, install Go and run go get:

$ go get -u github.com/tidwall/pretty

This will retrieve the library.

Pretty

Using this example:

{"name":  {"first":"Tom","last":"Anderson"},  "age":37,
"children": ["Sara","Alex","Jack"],
"fav.movie": "Deer Hunter", "friends": [
    {"first": "Janet", "last": "Murphy", "age": 44}
  ]}

The following code:

result = pretty.Pretty(example)

Will format the json to:

{
  "name": {
    "first": "Tom",
    "last": "Anderson"
  },
  "age": 37,
  "children": ["Sara", "Alex", "Jack"],
  "fav.movie": "Deer Hunter",
  "friends": [
    {
      "first": "Janet",
      "last": "Murphy",
      "age": 44
    }
  ]
}

Color

Color will colorize the json for outputing to the screen.

result = pretty.Color(json, nil)

Will add color to the result for printing to the terminal. The second param is used for a customizing the style, and passing nil will use the default pretty.TerminalStyle.

Ugly

The following code:

result = pretty.Ugly(example)

Will format the json to:

{"name":{"first":"Tom","last":"Anderson"},"age":37,"children":["Sara","Alex","Jack"],"fav.movie":"Deer Hunter","friends":[{"first":"Janet","last":"Murphy","age":44}]}```

Spec

Spec cleans comments and trailing commas from input JSON, converting it to valid JSON per the official spec: https://tools.ietf.org/html/rfc8259

The resulting JSON will always be the same length as the input and it will include all of the same line breaks at matching offsets. This is to ensure the result can be later processed by a external parser and that that parser will report messages or errors with the correct offsets.

The following example uses a JSON document that has comments and trailing commas and converts it prior to unmarshalling to using the standard Go JSON library.

data := `
{
  /* Dev Machine */
  "dbInfo": {
    "host": "localhost",
    "port": 5432,          // use full email address
    "username": "josh",
    "password": "pass123", // use a hashed password
  },
  /* Only SMTP Allowed */
  "emailInfo": {
    "email": "[email protected]",
    "password": "pass123",
    "smtp": "smpt.example.com",
  }
}
`

err := json.Unmarshal(pretty.Spec(data), &config)

Customized output

There's a PrettyOptions(json, opts) function which allows for customizing the output with the following options:

type Options struct {
	// Width is an max column width for single line arrays
	// Default is 80
	Width int
	// Prefix is a prefix for all lines
	// Default is an empty string
	Prefix string
	// Indent is the nested indentation
	// Default is two spaces
	Indent string
	// SortKeys will sort the keys alphabetically
	// Default is false
	SortKeys bool
}

Performance

Benchmarks of Pretty alongside the builtin encoding/json Indent/Compact methods.

BenchmarkPretty-16           1000000    1034 ns/op    720 B/op     2 allocs/op
BenchmarkPrettySortKeys-16    586797    1983 ns/op   2848 B/op    14 allocs/op
BenchmarkUgly-16             4652365     254 ns/op    240 B/op     1 allocs/op
BenchmarkUglyInPlace-16      6481233     183 ns/op      0 B/op     0 allocs/op
BenchmarkSpec-16             3200991     372 ns/op    352 B/op     1 allocs/op
BenchmarkSpecInPlace-16      4214520     282 ns/op      0 B/op     0 allocs/op
BenchmarkJSONIndent-16        450654    2687 ns/op   1221 B/op     0 allocs/op
BenchmarkJSONCompact-16       685111    1699 ns/op    442 B/op     0 allocs/op

These benchmarks were run on a MacBook Pro 2.4 GHz 8-Core Intel Core i9.

Contact

Josh Baker @tidwall

License

Pretty source code is available under the MIT License.