Deeply

A toolkit for deep structure manipulations, provides deep merge/clone functionality out of the box, and exposes hooks and custom adapters for more control and greater flexibility.

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Table of Contents

• Install
• Examples
  • Merging
    • Security concerns
  • Cloning
  • Arrays Custom Merging
    • Default Behavior
    • Combining Arrays
    • Appending Arrays
    • Appending Arrays and Keeping Unique Elements Only
    • Custom Merge Function
  • Cloning Functions
    • Cloning Prototype Chain
    • Extend Original Function Prototype
  • Custom flags and hooks
    • allowDangerousObjectKeys
    • useCustomAdapters
    • useCustomTypeOf
  • Mutable Operations
  • Ludicrous Mode
• Want to Know More?
• License

Install

$ npm install deeply --save

Examples

By default it provides interface for immutable operations, also available via explicit require require('deeply/immutable') or require('deeply').immutable property.

Merging

Deeply merges two or more objects.

var merge = require('deeply');

var result = merge({a: {a1: 1}}, {a: {a2: 2}}, {b: {b3: 3}});

assert.equal(result, {a: {a1: 1, a2: 2}, b: {b3: 3}});

Security concerns

Due to Prototype Pollution security vulnerability concerns, default behavior of when merging objects is to skip unsafe keys, like __proto__, please refer to the test/compatability.js file for code examples.

If there is a use case where such behavior is desired, pass allowDangerousObjectKeys flag to the context to skip keys safety checks.

var merge = require('deeply');
var result;

var context = { allowDangerousObjectKeys: merge.behaviors.allowDangerousObjectKeys };

result = merge.call(context, {}, JSON.parse('{"__proto__": {"a0": true}}'));
// end of the world, cats live with dogs...

Cloning

As degenerated case of merging one object on itself, it's possible to use deeply as deep clone function.

var merge = require('deeply');
var clone = merge;

var x = {a: {b: {c: 1}}};
var y = clone(x);

y.a.b.c = 2;

assert.equal(x.a.b.c, 1);

Arrays Custom Merging

By default array treated as primitive values and being replaced upon conflict, for more meaningful array merge strategy, provide one of the pre-built array merge helpers or a custom reduce function within invocation context.

Default Behavior

var merge = require('deeply');
var result = merge({ a: { b: [0, 2, 4, {a: 'A'}], c: 'first' }}, { a: {b: [1, 3, 5, {b: 'B'}], d: 'second' }});

assert.equal(result, { a: { b: [1, 3, 5, {b: 'B'}], c: 'first', d: 'second' }});

Combining Arrays

var merge = require('deeply');
var result;

var context =
{
  useCustomAdapters: merge.behaviors.useCustomAdapters,
  'array'          : merge.adapters.arraysCombine
};

// it might be useful when you have array of objects
result = merge.call(context, { a: { b: [0, {a: 'A1', b: 'B1'}, 4] }}, { a: {b: [1, {a: 'A2', c: 'C2'}, 5] }});
assert.equal(result, { a: { b: [1, {a: 'A2', b: 'B1', c: 'C2'}, 5] }});

Appending Arrays

var merge = require('deeply');

var context =
{
  useCustomAdapters: merge.behaviors.useCustomAdapters,
  'array'          : merge.adapters.arraysAppend
};

var result = merge.call(context, { a: { b: [0, 2, 4, 4, 2, 0] }}, { a: {b: [1, 3, 5, 5, 3, 1] }});

assert.equal(result, { a: { b: [0, 2, 4, 4, 2, 0, 1, 3, 5, 5, 3, 1] }});

Appending Arrays and Keeping Unique Elements Only

var merge = require('deeply');

var context =
{
  useCustomAdapters: merge.behaviors.useCustomAdapters,
  'array'          : merge.adapters.arraysAppendUnique
};

var result = merge.call(context, { a: { b: [0, 2, 4, 4, 2, 0] }}, { a: {b: [1, 3, 5, 5, 3, 1] }});

assert.equal(result, { a: { b: [0, 2, 4, 1, 3, 5] }});

Custom Merge Function

For example we need to have merging arrays to be appended, with only unique elements and sort the result array.

var merge = require('deeply');

var context =
{
  useCustomAdapters: merge.behaviors.useCustomAdapters,
  'array'          : appendUniqueAndSort
};

var result = merge.call(context, { a: { b: [0, 2, 4, 4, 2, 0] }}, { a: {b: [1, 3, 5, 5, 3, 1] }});

assert.equal(result, { a: { b: [0, 1, 2, 3, 4, 5] }});

// Custom array adapter
function appendUniqueAndSort(to, from, merge)
{
  // append only if new element isn't present yet
  from.forEach(function(v) { to.indexOf(v) == -1 && to.push(merge(undefined, v)); });

  // and sort
  return to.sort();
}

Cloning Functions

By default, functions copied as is to the result object, basically being treated as primitive values.

You can use functionsClone adapter to clone functions, creating new function object with the same signature as original.

var clone = require('deeply');

function subj(a, b)
{
  return a + b + 10;
}

subj.customProp = 13;

subj.prototype.A = 1;

subj.prototype.B = {isB: 'true'};

var context =
{
  useCustomAdapters: clone.behaviors.useCustomAdapters,
  'function'       : clone.adapters.functionsClone
};

var result = clone.call(context, { a: { b: subj}});

// cloned object function named subj
assert.equal(result, { a: { b: subj}});

// same signature
assert.equal(subj.name, result.a.b.name);
assert.equal(subj.length, result.a.b.length);

assert.equal(subj.customProp, result.a.b.customProp);

// separate objects
subj.isOriginal = true;
result.a.b.isCopy = true;

assert.equal(subj.isOriginal, true);
assert.equal(subj.isCopy, undefined);

assert.equal(result.a.b.isOriginal, undefined);
assert.equal(result.a.b.isCopy, true);

// same output
assert.equal(subj(3, 4), result.a.b(3, 4));

Cloning Prototype Chain

It will also clone prototype objects, so use this option with caution.

var clone = require('deeply');

function Subj()
{
  this.boom = 'Zap!';
}

Subj.prototype.A = 1;

Subj.prototype.B = {isB: 'true'};

var context =
{
  useCustomAdapters: clone.behaviors.useCustomAdapters,
  'function'       : clone.adapters.functionsClone
};

var result = clone.call(context, { class: Subj });

// cloned object function named Subj
assert.equal(result, { class: Subj });

// has prototype properties
assert.equal(result.class.prototype.A, 1);
assert.equal(result.class.prototype.B.isB, 'true');

// prototypes are decoupled
Subj.prototype.C = 2;
assert.equal(Subj.prototype.C, 2);
assert.equal(result.class.prototype.C, undefined);

// instances
var s1 = new Subj();
var s2 = new result.class();

assert.equal(s1.A, s2.A);
assert.equal(s1.B, s2.B);

assert.equal(s1.C, 2);
assert.equal(s2.C, undefined);

assert.equal(s1.boom, s2.boom);

// but reported instanceof isn't the same
assert.equal(s1 instanceof Subj, true);
assert.equal(s2 instanceof Subj, false);

Extend Original Function Prototype

When having proper instanceof results matters, you can use functionsExtend helper instead.

var clone = require('deeply');

function Subj()
{
  this.boom = 'Zap!';
  return this.boom;
}

Subj.customProp = 13;

Subj.prototype.A = 1;

Subj.prototype.B = {isB: 'true'};

var context =
{
  useCustomAdapters: clone.behaviors.useCustomAdapters,
  'function'       : clone.adapters.functionsExtend
};

var result = clone.call(context, { class: Subj });

// cloned object function named Subj
assert.equal(result, { class: Subj });

// same signature
assert.equal(Subj.name, result.class.name);
assert.equal(Subj.length, result.class.length);

assert.equal(Subj.customProp, result.class.customProp);

// separate objects
Subj.isOriginal = true;
result.class.isCopy = true;

assert.equal(Subj.isOriginal, true);
assert.equal(Subj.isCopy, undefined);

assert.equal(result.class.isOriginal, undefined);
assert.equal(result.class.isCopy, true);

// same output
assert.equal(Subj(), result.class());

// has prototype properties
assert.equal(result.class.prototype.A, 1);
assert.equal(result.class.prototype.B.isB, 'true');

// prototypes are extended
Subj.prototype.X = 67;
assert.equal(Subj.prototype.X, 67);
assert.equal(result.class.prototype.X, 67);

// instances
var s1 = new Subj();
var s2 = new result.class();

assert.equal(s1.A, s2.A);
assert.equal(s1.B, s2.B);

assert.equal(s1.boom, s2.boom);

// but reported instanceof isn't the same
assert.equal(s1 instanceof Subj, true);
assert.equal(s2 instanceof Subj, true);

Custom flags and hooks

allowDangerousObjectKeys

As shown in (Security Concerns)[#security-concerns] section, you can skip safety checks for unsafe object keys (e.g. __proto__) by passing allowDangerousObjectKeys flag to the context.

merge.call({ allowDangerousObjectKeys: merge.behaviors.allowDangerousObjectKeys }, {}, JSON.parse('{"__proto__": {"a0": true}}'));

useCustomAdapters

As shown in Custom Merge Function example, you can add custom adapters for any data type that supported by precise-typeof.

For this example we will combine arrays of number, by performing addition operation on array elements.

var merge = require('deeply');

var context =
{
  useCustomAdapters: merge.behaviors.useCustomAdapters,
  'array'          : merge.adapters.arraysCombine,
  'number'         : addNumbers
};

var result = merge.call(context, { a: { b: [0, 2, 4, 4, 2, 0] }}, { a: {b: [1, 3, 5, 5, 3, 1] }}, { a: {b: [7, 8, 9, 10, 11, 12] }});

assert.equal(result, { a: { b: [8, 13, 18, 19, 16, 13] }});

// Custom number adapter
function addNumbers(to, from)
{
  return (to || 0) + from;
}

useCustomTypeOf

In some cases you might need to have more control over type detection, for that you can supply your own type detection function.

In following example we'd use same precise-typeof library, but with pojoOnly: true flag:

var merge = require('deeply');
var typeOf = require('precise-typeof');
var moment = require('moment');

var context =
{
  useCustomTypeOf: merge.behaviors.useCustomTypeOf,
  'typeof'       : (input) => typeOf(input, {pojoOnly: true})
};

var result = merge.call(context, { a: {someField: 'value'}, b: 'other thing'}, { a: moment.utc('2018-11-27') });

assert.equal(result, { a: moment.utc('2018-11-27'), b: 'other thing' });

In the above example, it would treat moment object as atomic, and won't mix it's properties with other properties.

Mutable Operations

Mutable interface supports all the described operations, and available via explicit require require('deeply/mutable') or require('deeply').mutable property.

var merge = require('deeply/mutable');
var myObj = {a: {a1: 1, a2: 2}, b: {b1: 11, b2: 12}};

merge(myObj, {c: 'c', d: 'd'}, {x: {y: {z: -Infinity}}});

assert.equal(myObj, {a: {a1: 1, a2: 2}, b: {b1: 11, b2: 12}, c: 'c', d: 'd', x: {y: {z: -Infinity}}});

Ludicrous Mode

Also as shortcut and a homage to Tesla, ludicrous mode is available, that will clone functions and it's prototype objects by default. :) Details could be found in Cloning Functions examples.

var ludicrous = require('deeply/ludicrous');
var scopeVar = 6;

function original(a, b)
{
  return a + b + scopeVar;
}

var cloned = ludicrous({ func: original });

// cloned object function named subj
assert.equal(cloned, { func: original });

// same signature
assert.equal(original.name, cloned.func.name);
assert.equal(original.length, cloned.func.length);

// separate objects
original.isOriginal = true;
cloned.func.isCopy = true;

assert.equal(original.isOriginal, true);
assert.equal(original.isCopy, undefined);

assert.equal(cloned.func.isOriginal, undefined);
assert.equal(cloned.func.isCopy, true);

// same output
assert.equal(original(1, 2), cloned.func(1, 2));

Note: ludicrous isn't included into the main deeply package, so it won't be automatically pulled in, if you're bundling using browserify deeply/index.js, to use ludicrous in the browser you'd need to explicitly require it in your modules or specify direct path in your bundler config.

Want to Know More?

More examples can be found in test/compatability.js.

Or open an issue with questions and/or suggestions.

License

Deeply is released under the MIT license.