Irrelon Path

A powerful JSON path processor with no third-party dependencies. Allows you to traverse JSON object trees with a simple dot-delimited path format e.g. "obj.name"

What Can It Do?

Irrelon Path is a JavaScript object manipulation library that uses dot notation to denote object key / value field locations within the object structure. It allows you to easily access, modify or remove data from an object at locations specified via a path string.

Install

npm i @irrelon/path

Simple Usage

const {get} = require("@irrelon/path");

// Define an object in JSON
const obj = {
  "users": {
    "test1": {
      "name": "My Test User"
    }
  }
};

// Grab data from the object via the path solver
const result = get(obj, 'users.test1.name');

console.log(result); // Logs: My Test User

Escaping Fields with Periods

Sometimes you want to access data where a field name has periods in it like this:

const obj = {
  "users": {
    "[email protected]": {
      "name": "My Test User"
    }
  }
};

The user email address "[email protected]" contains a period that the path solver will interpret as a traversal indicator. If we try to ask the path solver to get the data in the key "[email protected]" it will look for a field called "test@test" with a sub-field "com".

To avoid this, escape the period using the escape() function:

const {get, escape} = require("@irrelon/path");
const result = get(obj, `users.${escape('[email protected]')}.name`);

console.log(result); // Logs: My Test User

Behaviour

If data or an object to traverse does not exist inside the base object, the path solver will return undefined and will NOT throw an error:

const {get} = require("@irrelon/path");

const obj = {
  "foo": null
};

const result = get(obj, "foo.bar.one");

console.log(result); // Logs: undefined

Default Values

When using get() you can specify a default value to return if the value at the given path is undefined.

const {get} = require("@irrelon/path");

const obj = {
  "foo": null
};

const result = get(obj, "foo.bar.one", "My Default Value");

console.log(result); // Logs: My Default Value

Methods

get (obj, path, defaultValue)

|Param|Type|Required|Default| |---|---|---|---| |obj|Object or Array|true|none| |path|String|true|none| |defaultValue|Any|false|undefined|

Gets a value from the obj at the given path and if no value exists for that path, returns defaultValue if one was provided.

const {get} = require("@irrelon/path");

const obj = {
  "foo": null
};

const result1 = get(obj, "foo");
const result2 = get(obj, "foo.bar.one", "My Default Value");

console.log(result1); // Logs: null
console.log(result2); // Logs: My Default Value

If you want to access elements of an array, simply use the element index as part of your path e.g.

const {get} = require("@irrelon/path");

const obj = {
    "myArr": [
        "hello",
        {
            "bar": "goodbye"
        }
    ]
};

const result1 = get(obj, "myArr.0"); // hello
const result2 = get(obj, "myArr.1.bar"); // goodbye

set (obj, path, value)

|Param|Type|Required|Default| |---|---|---|---| |obj|Object or Array|true|none| |path|String|true|none| |value|Any|true|none|

Sets a value in the obj at the given path.

If the given path doesn't exist in the target object it will be created by making each non-existent path part a new object.

const {set, get} = require("@irrelon/path");

const obj = {
  "foo": null
};

const result1 = get(obj, "foo.bar"); // Currently: undefined

set(obj, "foo.bar", "hello");

const result2 = get(obj, "foo.bar");

console.log(result1); // Logs: undefined
console.log(result2); // Logs: hello

setImmutable (obj, path, value)

This is a helper function that calls set() with immutable flag switched on.

|Param|Type|Required|Default| |---|---|---|---| |obj|Object or Array|true|none| |path|String|true|none| |value|Any|true|none|

Sets a value in the obj at the given path in an immutable way and returns a new object. This will not change or modify the existing obj.

Keep in mind that references to objects that were not modified by the operation remain the same. This allows systems like React to appropriately act on changes to specific data rather than re-rendering an entire DOM tree when one sub-object changes.

If the given path doesn't exist in the target object it will be created by making each non-existent path part a new object.

const {setImmutable, get} = require("@irrelon/path");

const obj = {
  "foo": {
  	"bar": "goodbye",
  	"subBar": {
  		"somethingElse": true
  	}
  },
  "otherObj": {
  	"enabled": true
  }
};

const result1 = get(obj, "foo.bar"); // Currently: goodbye

const newObj = setImmutable(obj, "foo.bar", "hello");

// Original object remains unmodified (will still be "goodbye");
const result2 = get(obj, "foo.bar");

// New object has new value of "hello"
const result3 = get(newObj, "foo.bar");

console.log(result1); // Logs: goodbye
console.log(result2); // Logs: goodbye
console.log(result3); // Logs: hello

// Objects that did not have any modifications remain the same
// and still share a reference in memory
console.log(obj.otherObj === newObj.otherObj); // Logs: true

// Objects that did have modifications will not be the same
console.log(obj.foo === newObj.foo); // Logs: false

// Child objects of modified parents will still have references
// to the original since the child object wasn't modified directly
console.log(obj.foo.subBar === newObj.foo.subBar); // Logs: true

unSet (obj, path)

Deletes a key from an object by the given path.

const obj = {
	"foo": {
		"bar": [{
			"moo": true,
			"baa": "ram you"
		}]
	}
};

console.log(obj.foo.bar[0].baa); // Logs: ram you

unSet(obj, "foo.bar.0.baa");

console.log(obj.foo.bar[0].baa); // Logs: undefined
console.log(obj.foo.bar[0].hasOwnProperty("baa")); // Logs: false

update (obj, updateData, options)

Sets a single value on the passed object and given path. This will directly modify the "obj" object. If you need immutable updates, use updateImmutable() instead.

const obj = {
	"foo": {
		"bar": [{
			"moo": true,
			"baa": "ram you"
		}]
	}
};

console.log(obj.foo.bar[0].baa); // Logs: ram you

update(obj, {
	"foo.bar.0.baa": "hello I've been updated",
	"and.so": "have I!"
});

console.log(obj.foo.bar[0].baa); // Logs: hello I've been updated
console.log(obj.and.so); // Logs: have I!

clean (str)

Removes leading period (.) from string and returns new string.

countLeafNodes (obj)

Counts the total number of key leaf nodes in the passed obj. Leaf nodes are values in the object tree that cannot contain other key/values (so are not objects or arrays).

const {countLeafNodes} = require("@irrelon/path");

const obj = {
  "foo": {
  	"bar": "goodbye",
  	"subBar": {
  		"somethingElse": true
  	}
  },
  "otherObj": {
  	"enabled": true
  }
};

const result = countLeafNodes(obj);

console.log(result); // Logs: 3 (foo.bar, foo.subBar.somthingElse, otherObj.enabled)

findOnePath (source, query)

Finds the first item that matches the structure of query and returns the path to it

const {findOnePath} = require("@irrelon/path");

const myDataArray = [{
  "profile": {
  	"id": 1,
  	"name": "Ron Swanson"
  }
}, {
 "profile": {
	"id": 2,
	"name": "April Ludgate"
 }
}];

// Find the object that has a key "profile"
// with a object that has a key "_id" that 
// has a value 1, and return the path to it
const result1 = findOnePath(myDataArray, {
	profile: {
		_id: 1
	}
});

console.log(result1); // Logs: "0"

// Find the object that has a key "_id" that 
// has a value 1, and return the path to it
const result2 = findOnePath(myDataArray, {
	_id: 1
});

console.log(result2); // Logs: "0.profile"

See the unit tests for findOnePath() for many more examples of usage.

diff (obj1, obj2, path, strict, maxDepth)

|Param|Type|Required|Default| |---|---|---|---| |obj1|Object or Array|true|none| |obj2|Object or Array|true|none| |path|String|false|""| |strict|Boolean|false|false| |maxDepth|Number|false|Infinity|

Compares two objects / arrays and returns the differences as an array of paths to the different fields.

Fields are considered "different" if they do not contain equal values. The equality check is either strict or non-strict based on the strict argument.

It is important to understand that this function detects differences between field values, not differences between object structures. For instance if a field in obj1 contains undefined and obj2 does not contain that field at all, it's value in obj2 will also be undefined so there would be no difference detected.

const {diff} = require("@irrelon/path");

const obj1 = {
	"user": {
		"_id": 1,
		"firstName": "Jimbo",
		"lastName": "Jetson"
  	}
};

const obj2 = {
	"user": {
		"_id": "1", // Notice string instead of numerical _id
		"firstName": "James", // We also changed the name from "Jimbo" to "James"
		"lastName": "Jetson"
  	}
};

const resultArr1 = diff(obj1, obj2, "", false); // Non-strict equality check
const resultArr2 = diff(obj1, obj2, "", true); // Strict equality check

console.log(resultArr1); // Logs: ["user.firstName"]
console.log(resultArr2); // Logs: ["user._id", "user.firstName"]

Version 3.x Breaking Changes

There was a bug in the get() function that would return an incorrect value when a non-object was passed to get data from and a path was passed e.g.

get("foo-im-not-an-object", "some.path.to.get.data.from"); // Version 2.x returned "foo-im-not-an-object"

In version 3.x, this call will return undefined as expected.

Version 2.x Breaking Changes

Version 1.x exported a class that you could instantiate. Version 2.x exports an object with all available functions. You can require version 2.x either all at once (all functions) or you can destructure to require only the functions you need. This change is primarily to support tree shaking, as well as move to a more functional programming style, albeit not pure functional style :)

Version 2.x is a breaking change from version 1.x and you will need to migrate your code to work with the new version. Migration is fairly simple and instead of using an instance of the 1.x class, you simply require the parts of the library you need e.g.

Version 1.x Style Code (Don't Do This)

// DON'T DO THIS !!!!!!!!!!!
const Path = require("irrelon-path");
const pathSolver = new Path();
const a = {hello: {foo: true}};
const b = pathSolver.get(a, "hello.foo"); // b === true

Version 2.x Style Code (Please Use This)

// DO THIS :)
const {get} = require("@irrelon/path");
const a = {hello: {foo: true}};
const b = get(a, "hello.foo"); // b === true