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JSON Toolkit

This is a simple toolkit to make life with JSON easier in Node. On top of traditional parse and stringify methods, this toolkit helps retrieve JSON and traverse keys/values.


npm install json-toolkit --save

The --save will tell npm is add it to your package.json.


To use, simply require the package. JSON-Toolkit also has a Resource class (which is really the bulk of this thing) which is attached to the main object.

var json = require("json-toolkit"),
	JSONR = json.Resource;

API Documentation

json.parse( str )

Parses str into Javascript. Internally uses jsonlint.parse. Throws any validation errors.

json.validate( str )

Attempts to parses str into Javascript and uses jsonlint to validate. If a validation error is found, it is returned. Otherwise, null is returned on valid JSON.

json.stringify( obj [, replacer [, indent ] ] )

Parses a obj into JSON. Internally uses JSON.stringify.

json.prettify( obj [, indent ] )

Parses a obj into formatted JSON. indent is a string to use for indents or a number for the amount of spaces in an indent. Default for indent is \t.

json.parseFile( file, callback )

Gets file contents and parses into Javascript. callback gives two arguments, error and data.

json.saveToFile( data, file [, indent ] [, callback ] )

Parses data as JSON and saves to file. Using indent forces formatted printing (see above for usage). callback is called with one argument, error.

This method used to be saveJSON(). The name was changed to better represent what it does. Both functions will do the same thing.

new (json.Resource)( file | JSON | data [, options ] )

Creates a new Resource object. The constructor's first argument will take anything. If it's a string, it assumes that it is raw JSON or a filename (see options). If it's falsy, the internal data is set to {}. If it's anything else, it uses that.

Resource extends the Node class EventEmitter and has several events to capture. If using a filename in the constructor, you must capture the "ready" event before the object can be used. This class used to be named Helper and is still accessible by that handle.

One major thing to point out is that this uses path keys to traverse the data object. Anytime a method below has an argument named key, you can retrieve "deep" information by creating a "path" to it. This path is seperated by the option key_sep. Example: get("dependencies:underscore") -> data["dependencies"]["underscore"]


  • from_file, Default: false, Tells Resource that first argument into constructor is a filename and not raw JSON. Must wait for "ready" event before the object is usable. If the file doesn't exist, the object ignores that, assuming you are creating a new JSON document.
  • key_sep, Default: :, The string seperator used to divide paths.
  • pretty_output, Default: false, When saving, print formatted JSON.
  • indent, Default: \t, When turning this object into formatted JSON, this string is used as the indent. (See above)


  • data : Holds all of the parsed JSON data.
  • file : Name of the file to save to. This is set on construction and each save.


  • ready : Emitted when the object is ready for use. Not necesary unless using a file for data instead of a string or an object. Actually, any "ready" event you declare while using synchronous operations (ie, no FS calls) won't be fast enough and likely won't ever be called.
  • error : Emitted when object encouters an error. It should be noted that errors have the possibility of being thrown and not captured by this event. If you come across one, please let me know.
  • change : Emitted when a key is set. Gives two arguments, keys, which is an string path and value.
  • load : Emitted when object completes a load. Gives a single argument, old_data which is an object representing the previous state of data.
  • save : Emitted when a file is successfully saved. Gives a single argument, file.


get( key )

Retrieves the value at key in data. To transcend objects, seperate each key with key_sep.

set( key, value )

Sets value at key in data.

test( key, t )

Test the value at key against t. If t is a string, then it is used in a typeof to test the value as a specifc type. If t is a function, then it is called with value as the only argument. If t is a regular expression, the value is tested for matches. Anything else is matched for equality.

For example, test("dependencies:underscore", "string") would return true on this module's package.json.

match( key )

Returns an array of all keys (deeply) that match key. On top of using the "path" for key, match introduces two special characters: * and **. A single * will match anything up to the next key_sep. A **, however, will match anything including key_sep.

For example, deps:* would match deps:underscore and deps:foo, but not deps or deps:foo:bar. deps** would match deps and deps:foo and deps:foo:bar but not foo:deps.

This method turns string key into a Regular Expression so any valid regex in key is compatible. This method will also accept a Regular Expression for key and will be significantly faster than using a string.

each( [ match, ] iterative )

Loops through all keys returned from match (see above) and calls iterative for each key. iterative is a function with three arguments, value, key, and list. This is useful when trying to dynamically process keys/values, however it is very inefficient and should not be your "go-to" loop.

replace( [ match, ] value )

Loops through all keys returned from match (see above) and sets them to value. value can also an iterative function that should return a new value for the key. It is called with three arguments, value, key, and list.

watch( [ match, ] callback )

Waits for changes on keys that match and calls callback with two arguments: key and value.

find( value )

Deeply search data for value and return the first key that matches.

search( value )

Deeply search data for value and return all keys that match.

load( data [, callback ] )

Extends the internal data with data (not deep). If callback is passed, data is assumed to be a filename and this will instead retrieve and parse JSON. The constructor uses this to handle the first argument.

save( [ file ] [, callback ] )

Saves data as JSON to file. If file is not provided, the internal file property is used instead. On completion, the internal file property is set to file. callback is called with one argument, error.

toPrettyString( [ indent ] )

Returns a formatted JSON string. indent is optional and by default will use options.indent.


Returns an unformatted JSON string.


Returns internal data object. This is useful for embedding into objects that will be converted into JSON.


Basic usage with the JSON Resource.

var job = new JSONR("package.json", {
    from_file: true,
    pretty_output: true
job.on("ready", function() { // Wait for file to import 
    job.set("dependencies:underscore", "1.4.4"); // Set a single key 
    job.replace("dependencies:*", function(v, k) { // Set a key by match 
        console.log(k, "=>", v);
        return '9.9.9';
    });; // Save the file 
job.on("save", function(file) { // When save is successfuly 
    console.log("Saved JSON to "+file+".");
job.on("error", function(err) { // When an error is thrown 

Loading and watching.

// New Resource, file doesn't exist so ignore that for saving later 
var h = new JSONR('asdf.json', { from_file: true, pretty_output: true });
h.on("ready", function() {
    h.load("package.json", function(err) { // Load the current package.json 
        if (err) return console.log(err.stack);"dependencies:*", function(key, value) { // Watch for any changes on dependencies 
            console.log("Changed " + key + " to " + value);
        // Some time later... 
        setTimeout(function() {
            h.set("dependencies:underscore", "9.9.9");
            h.set("dependencies:jsonlint", "9.9.9");
        }, 3000);


I really want to extend this library to include many different JSON tools. These are only the ones that I have personally needed in the past. If you have a suggested addition to this library, I'd love to hear it (and probably add it). Of course, I (Tyler Johnson) am always reachable at