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set a json value quickly

SJSON is a Go package that provides a very fast and simple way to set a value in a json document. The purpose for this library is to provide efficient json updating for the SummitDB project. For quickly retrieving json values check out GJSON.

For a command line interface check out JSONed.

Getting Started

Installing

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

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

This will retrieve the library.

Set a value

Set sets the value for the specified path. A path is in dot syntax, such as "name.last" or "age". This function expects that the json is well-formed and validated. Invalid json will not panic, but it may return back unexpected results. Invalid paths may return an error.

package main

import "github.com/tidwall/sjson"

const json = `{"name":{"first":"Janet","last":"Prichard"},"age":47}`

func main() {
	value, _ := sjson.Set(json, "name.last", "Anderson")
	println(value)
}

This will print:

{"name":{"first":"Janet","last":"Anderson"},"age":47}

Path syntax

A path is a series of keys separated by a dot. The dot and colon characters can be escaped with ''.

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

"name.last"          >> "Anderson"
"age"                >> 37
"children.1"         >> "Alex"
"friends.1.last"     >> "Craig"

The -1 key can be used to append a value to an existing array:

"children.-1"  >> appends a new value to the end of the children array

Normally number keys are used to modify arrays, but it's possible to force a numeric object key by using the colon character:

{
  "users":{
    "2313":{"name":"Sara"},
    "7839":{"name":"Andy"}
  }
}

A colon path would look like:

"users.:2313.name"    >> "Sara"

Supported types

Pretty much any type is supported:

sjson.Set(`{"key":true}`, "key", nil)
sjson.Set(`{"key":true}`, "key", false)
sjson.Set(`{"key":true}`, "key", 1)
sjson.Set(`{"key":true}`, "key", 10.5)
sjson.Set(`{"key":true}`, "key", "hello")
sjson.Set(`{"key":true}`, "key", map[string]interface{}{"hello":"world"})

When a type is not recognized, SJSON will fallback to the encoding/json Marshaller.

Examples

Set a value from empty document:

value, _ := sjson.Set("", "name", "Tom")
println(value)

// Output:
// {"name":"Tom"}

Set a nested value from empty document:

value, _ := sjson.Set("", "name.last", "Anderson")
println(value)

// Output:
// {"name":{"last":"Anderson"}}

Set a new value:

value, _ := sjson.Set(`{"name":{"last":"Anderson"}}`, "name.first", "Sara")
println(value)

// Output:
// {"name":{"first":"Sara","last":"Anderson"}}

Update an existing value:

value, _ := sjson.Set(`{"name":{"last":"Anderson"}}`, "name.last", "Smith")
println(value)

// Output:
// {"name":{"last":"Smith"}}

Set a new array value:

value, _ := sjson.Set(`{"friends":["Andy","Carol"]}`, "friends.2", "Sara")
println(value)

// Output:
// {"friends":["Andy","Carol","Sara"]

Append an array value by using the -1 key in a path:

value, _ := sjson.Set(`{"friends":["Andy","Carol"]}`, "friends.-1", "Sara")
println(value)

// Output:
// {"friends":["Andy","Carol","Sara"]

Append an array value that is past the end:

value, _ := sjson.Set(`{"friends":["Andy","Carol"]}`, "friends.4", "Sara")
println(value)

// Output:
// {"friends":["Andy","Carol",null,null,"Sara"]

Delete a value:

value, _ := sjson.Delete(`{"name":{"first":"Sara","last":"Anderson"}}`, "name.first")
println(value)

// Output:
// {"name":{"last":"Anderson"}}

Delete an array value:

value, _ := sjson.Delete(`{"friends":["Andy","Carol"]}`, "friends.1")
println(value)

// Output:
// {"friends":["Andy"]}

Delete the last array value:

value, _ := sjson.Delete(`{"friends":["Andy","Carol"]}`, "friends.-1")
println(value)

// Output:
// {"friends":["Andy"]}

Contact

Josh Baker @tidwall

License

SJSON source code is available under the MIT License.

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