mpath

What is mpath?

The mpath npm package is a utility for getting and setting values of nested properties in JavaScript objects using dot notation or array paths. It is particularly useful for manipulating deeply nested objects without having to write complex and repetitive code.

What are mpath's main functionalities?

Get Value

This feature allows you to retrieve the value of a nested property within an object using a dot notation path.

const mpath = require('mpath');
const obj = { a: { b: { c: 42 } } };
const value = mpath.get('a.b.c', obj);
console.log(value); // 42

Set Value

This feature allows you to set the value of a nested property within an object using a dot notation path.

const mpath = require('mpath');
const obj = { a: { b: { c: 42 } } };
mpath.set('a.b.c', 100, obj);
console.log(obj.a.b.c); // 100

Unset Value

This feature allows you to unset (delete) a nested property within an object using a dot notation path.

const mpath = require('mpath');
const obj = { a: { b: { c: 42 } } };
mpath.unset('a.b.c', obj);
console.log(obj.a.b.c); // undefined

Has Value

This feature allows you to check if a nested property exists within an object using a dot notation path.

const mpath = require('mpath');
const obj = { a: { b: { c: 42 } } };
const hasValue = mpath.has('a.b.c', obj);
console.log(hasValue); // true

Other packages similar to mpath

lodash

Lodash is a popular utility library that provides a wide range of functions for manipulating arrays, objects, and other data types. It includes methods like _.get, _.set, and _.has which offer similar functionality to mpath for working with nested properties.

dot-prop

Dot-prop is a small utility for getting, setting, and deleting nested properties in JavaScript objects using dot notation. It is similar to mpath but is more lightweight and focused solely on property manipulation.

object-path

Object-path is a utility for accessing and manipulating deep properties in JavaScript objects. It provides methods like get, set, and del, which are similar to mpath's functionality but also includes additional features like ensuring paths exist.

README

#mpath

{G,S}et javascript object values using MongoDB-like path notation.

###Getting

var mpath = require('mpath');

var obj = {
    comments: [
      { title: 'funny' },
      { title: 'exciting!' }
    ]
}

mpath.get('comments.1.title', obj) // 'exciting!'

mpath.get supports array property notation as well.

var obj = {
    comments: [
      { title: 'funny' },
      { title: 'exciting!' }
    ]
}

mpath.get('comments.title', obj) // ['funny', 'exciting!']

Array property and indexing syntax, when used together, are very powerful.

var obj = {
  array: [
      { o: { array: [{x: {b: [4,6,8]}}, { y: 10} ] }}
    , { o: { array: [{x: {b: [1,2,3]}}, { x: {z: 10 }}, { x: 'Turkey Day' }] }}
    , { o: { array: [{x: {b: null }}, { x: { b: [null, 1]}}] }}
    , { o: { array: [{x: null }] }}
    , { o: { array: [{y: 3 }] }}
    , { o: { array: [3, 0, null] }}
    , { o: { name: 'ha' }}
  ];
}

var found = mpath.get('array.o.array.x.b.1', obj);

console.log(found); // prints..

    [ [6, undefined]
    , [2, undefined, undefined]
    , [null, 1]
    , [null]
    , [undefined]
    , [undefined, undefined, undefined]
    , undefined
    ]

#####Field selection rules:

The following rules are iteratively applied to each segment in the passed path. For example:

var path = 'one.two.14'; // path
'one' // segment 0
'two' // segment 1
14    // segment 2

• 1. when value of the segment parent is not an array, return the value of parent.segment
• 1. when value of the segment parent is an array
  • a) if the segment is an integer, replace the parent array with the value at parent[segment]
  • b) if not an integer, keep the array but replace each array item with the value returned from calling get(remainingSegments, item) or undefined if falsey.

#####Maps

mpath.get also accepts an optional map argument which receives each individual found value. The value returned from the map function will be used in the original found values place.

var obj = {
    comments: [
      { title: 'funny' },
      { title: 'exciting!' }
    ]
}

mpath.get('comments.title', obj, function (val) {
  return 'funny' == val
    ? 'amusing'
    : val;
});
// ['amusing', 'exciting!']

###Setting

var obj = {
    comments: [
      { title: 'funny' },
      { title: 'exciting!' }
    ]
}

mpath.set('comments.1.title', 'hilarious', obj)
console.log(obj.comments[1].title) // 'hilarious'

mpath.set supports the same array property notation as mpath.get.

var obj = {
    comments: [
      { title: 'funny' },
      { title: 'exciting!' }
    ]
}

mpath.set('comments.title', ['hilarious', 'fruity'], obj);

console.log(obj); // prints..

  { comments: [
      { title: 'hilarious' },
      { title: 'fruity' }
  ]}

Array property and indexing syntax can be used together also when setting.

var obj = {
  array: [
      { o: { array: [{x: {b: [4,6,8]}}, { y: 10} ] }}
    , { o: { array: [{x: {b: [1,2,3]}}, { x: {z: 10 }}, { x: 'Turkey Day' }] }}
    , { o: { array: [{x: {b: null }}, { x: { b: [null, 1]}}] }}
    , { o: { array: [{x: null }] }}
    , { o: { array: [{y: 3 }] }}
    , { o: { array: [3, 0, null] }}
    , { o: { name: 'ha' }}
  ]
}

mpath.set('array.1.o', 'this was changed', obj);

console.log(require('util').inspect(obj, false, 1000)); // prints..

{
  array: [
      { o: { array: [{x: {b: [4,6,8]}}, { y: 10} ] }}
    , { o: 'this was changed' }
    , { o: { array: [{x: {b: null }}, { x: { b: [null, 1]}}] }}
    , { o: { array: [{x: null }] }}
    , { o: { array: [{y: 3 }] }}
    , { o: { array: [3, 0, null] }}
    , { o: { name: 'ha' }}
  ];
}

mpath.set('array.o.array.x', 'this was changed too', obj);

console.log(require('util').inspect(obj, false, 1000)); // prints..

{
  array: [
      { o: { array: [{x: 'this was changed too'}, { y: 10, x: 'this was changed too'} ] }}
    , { o: 'this was changed' }
    , { o: { array: [{x: 'this was changed too'}, { x: 'this was changed too'}] }}
    , { o: { array: [{x: 'this was changed too'}] }}
    , { o: { array: [{x: 'this was changed too', y: 3 }] }}
    , { o: { array: [3, 0, null] }}
    , { o: { name: 'ha' }}
  ];
}

####Setting arrays

By default, setting a property within an array to another array results in each element of the new array being set to the item in the destination array at the matching index. An example is helpful.

var obj = {
    comments: [
      { title: 'funny' },
      { title: 'exciting!' }
    ]
}

mpath.set('comments.title', ['hilarious', 'fruity'], obj);

console.log(obj); // prints..

  { comments: [
      { title: 'hilarious' },
      { title: 'fruity' }
  ]}

If we do not desire this destructuring-like assignment behavior we may instead specify the $ operator in the path being set to force the array to be copied directly.

var obj = {
    comments: [
      { title: 'funny' },
      { title: 'exciting!' }
    ]
}

mpath.set('comments.$.title', ['hilarious', 'fruity'], obj);

console.log(obj); // prints..

  { comments: [
      { title: ['hilarious', 'fruity'] },
      { title: ['hilarious', 'fruity'] }
  ]}

####Field assignment rules

The rules utilized mirror those used on mpath.get, meaning we can take values returned from mpath.get, update them, and reassign them using mpath.set. Note that setting nested arrays of arrays can get unweildy quickly. Check out the tests for more extreme examples.

#####Maps

mpath.set also accepts an optional map argument which receives each individual value being set. The value returned from the map function will be used in the original values place.

var obj = {
    comments: [
      { title: 'funny' },
      { title: 'exciting!' }
    ]
}

mpath.set('comments.title', ['hilarious', 'fruity'], obj, function (val) {
  return val.length;
});

console.log(obj); // prints..

  { comments: [
      { title: 9 },
      { title: 6 }
  ]}

Custom object types

Sometimes you may want to enact the same functionality on custom object types that store all their real data internally, say for an ODM type object. No fear, mpath has you covered. Simply pass the name of the property being used to store the internal data and it will be traversed instead:

var mpath = require('mpath');

var obj = {
    comments: [
      { title: 'exciting!', _doc: { title: 'great!' }}
    ]
}

mpath.get('comments.0.title', obj, '_doc')            // 'great!'
mpath.set('comments.0.title', 'nov 3rd', obj, '_doc')
mpath.get('comments.0.title', obj, '_doc')            // 'nov 3rd'
mpath.get('comments.0.title', obj)                    // 'exciting'

When used with a map, the map argument comes last.

mpath.get(path, obj, '_doc', map);
mpath.set(path, val, obj, '_doc', map);

LICENSE