flatten-obj

flatten-obj

Converts an object literal with deeply nested nodes to a simple key/value object. In other words converts this:

{
  foo: 1,
  bar: {
    sub1: 2,
    sub2: {
      sub3: 3
    }
  }
}

To this:

{
  foo: 1,
  'bar.sub1': 2,
  'bar.sub2.sub3': 3
}

Installation

npm install flatten-obj

Usage

var flatten = require('flatten-obj')()

var obj = {
  foo: {
    bar: 1
  }
}

// outputs `{ 'foo.bar': 1 }`
console.log(flatten(obj))

Blacklist

Some objects migth seem like object literals, but shouldn't be flattened. To avoid this, you can supply a list of classes that shouldn't be flattened when the object is traversed:

var Klass = function () {
  this.baz = 1
}

var flatten = require('flatten-obj')({ blacklist: [Klass] })

var obj = {
  foo: {
    bar: new Klass()
  }
}

// outputs `{ 'foo.bar': { baz: 1 } }`
console.log(flatten(obj))

Custom separator

You can use a custom separator character to join keys:

var flatten = require('flatten-obj')({ separator: '/' })

var obj = {
  foo: {
    bar: 42
  }
}

// outputs `{ 'foo/bar': 42 }`
console.log(flatten(obj))

Leaves

Only return the leaf nodes

var flatten = require('flatten-obj')({ onlyLeaves: true })

var obj = {
  sub: {
    foo: 1,
    bar: {
      baz: 2
    }
  }
}

// outputs `{ foo: 1, baz: 2 }`
console.log(flatten(obj))

Gotchas

MongoDB data types

MongoDB data types like ObjectId or Timestamp looks like regular object literals and should be handled with care. So you would normally want to add those to the blacklist:

var mongodb = require('mongodb')
var flatten = require('flatten-obj')({ blacklist: [
  mongodb.ObjectID,
  mongodb.DBRef,
  mongodb.Timestamp,
  mongodb.MinKey,
  mongodb.MaxKey,
  mongodb.Long
]})

Arrays

This module currenly leaves arrays and their content in place. I.e. the keys foo and bar in the following object isn't modified:

{
  foo: [1, 2, 3],
  bar: [{ foo: 1 }, { bar: 2 }]
}

If you are familiar with MongoDB you know though that it's possible to update single elements of an array using the dot-notation-syntax.

Open a pull request or tell me about your use case if you'd like the above object to be converted to:

{
  foo: [1, 2, 3],
  'bar.0.foo': 1,
  'bar.1.bar': 2
}

License

MIT