AngularJS: comparing the differences between copying and extending

Question

AngularJS: comparing the differences between copying and extending

Explaining Different Object Copy Methods :

When it comes to copying objects in certain situations, two common solutions are often considered: using angular.copy() or angular.extend().

Challenge I Am Currently Facing :

The

angular.copy(source, destination)

method creates a deep copy of the source object and assigns it to the destination. This means that modifications made to the source object do not affect the destination object.

Code for Deep Copy :

var mySource = {'name' : 'Beta', 'age' : '24'}
var myDest = {}
angular.copy(mySource,myDest);
mySource.name = "Alpha";
console.log(mySource); // Object {name: "Alpha", age: "24"}
console.log(myDest); // Object {name: "Beta", age: "24"}
console.log(mySource.obj === myDest.obj); // false

However, with

angular.extend(destination, source)

, a shallow copy is created where both source and destination point to the same address. Therefore, modifying the source will also reflect in the destination object, contrary to what might be expected.

Code for Shallow Copy :

var mySource = {'name' : 'Beta', 'age' : '24'}
var myDest = {}
angular.extend(myDest,mySource);
mySource.name = "Alpha";
console.log(mySource); // Object {name: "Alpha", age: "24"}
console.log(myDest); // Object {name: "Beta", age: "24"}
console.log(mySource.obj === myDest.obj); // True

For further reference, you can view this jsfiddle link: https://jsfiddle.net/U3pVM/24322/

If anyone could provide insight on the proper usage of angular.copy() & angular.extend(), it would be greatly appreciated as I am new to these concepts. Thank you.

javascript angularjs deep-copy shallow-copy

Answer 1

Answer №1

I made some updates to the code. Now, the angular.extends function is functioning as expected. It's important to note that when you provide an empty object as the first parameter (destination) in angular.extends and then add the source, Angular will keep both objects intact and only copy over the properties, much like angular.copy does.

// angular.copy()

var mySource = {'name' : 'sakshi', 'age' : '24', 'obj' :{'key':'value'}}
var myDest = angular.copy(mySource);

mySource.name = "Beta";
console.log(mySource); // Object {name: "Beta", age: "24", obj: Object}
console.log(myDest); // Object {name: "sakshi", age: "24", obj: Object}
console.log(mySource.obj === myDest.obj); // false

// angular.extend()

var mySource = {'name' : 'sakshi', 'age' : '24', 'obj' :{'key':'value'}}
var myDest = angular.extend(mySource);
mySource.name = "Beta";
console.log(mySource); // Object {name: "Beta", age: "24", obj: Object}
console.log(myDest); // Object {name: "Beta", age: "24", obj: Object}
console.log(mySource.obj === myDest.obj); // True

Answer 2

I made some updates to the code. Now, the angular.extends function is functioning as expected. It's important to note that when you provide an empty object as the first parameter (destination) in angular.extends and then add the source, Angular will keep both objects intact and only copy over the properties, much like angular.copy does.

// angular.copy()

var mySource = {'name' : 'sakshi', 'age' : '24', 'obj' :{'key':'value'}}
var myDest = angular.copy(mySource);

mySource.name = "Beta";
console.log(mySource); // Object {name: "Beta", age: "24", obj: Object}
console.log(myDest); // Object {name: "sakshi", age: "24", obj: Object}
console.log(mySource.obj === myDest.obj); // false

// angular.extend()

var mySource = {'name' : 'sakshi', 'age' : '24', 'obj' :{'key':'value'}}
var myDest = angular.extend(mySource);
mySource.name = "Beta";
console.log(mySource); // Object {name: "Beta", age: "24", obj: Object}
console.log(myDest); // Object {name: "Beta", age: "24", obj: Object}
console.log(mySource.obj === myDest.obj); // True

Answer 3

Answer №2

agular.copy is a method that creates a deep copy of an object, meaning it generates a new object with the same values. On the other hand, angular.extend only performs a shallow copy, so the attributes point to the same values in memory. If you want a detailed explanation about the differences between .copy(), .extend(), and .merge() methods, check out this resource.

Answer 4

agular.copy is a method that creates a deep copy of an object, meaning it generates a new object with the same values. On the other hand, angular.extend only performs a shallow copy, so the attributes point to the same values in memory. If you want a detailed explanation about the differences between .copy(), .extend(), and .merge() methods, check out this resource.

Answer 5

Answer №3

Understanding the concept of copying versus extending is important when dealing with primitives in JavaScript.

Copying:

When copying, each property of an object is iterated through. If the property is a primitive value, it is simply copied. If it is an object, a new object is created and a recursive copy is performed.

The following is a basic implementation of the copy function:

function copy(destination, source) {
  for (var prop in source) {
    if (typeof source[prop] === 'object') {
      var clone = {};
      copy(clone, source[prop]);
      destination[prop] = clone;
    } else {
      // copy the primitive
      destination[prop] = source[prop];
    }
  }
}

Extending:

Extending also iterates through each property of an object. If the property is a primitive value, it is copied. If it is an object, a reference to the original object is created instead of creating a new one.

function extend(destination, source) {
  for (var prop in source) {
    destination[prop] = source[prop];
  }
}

It's important to note that when performing a shallow copy, primitives are always cloned. To avoid this, you can change properties of a referenced object achieved through a shallow copy.

var mySource = {person: {'name' : 'Beta', 'age' : '24'}}
var myDest = {}
extend(myDest,mySource);
mySource.person.name = "Alpha";
console.log(mySource); // Output: Object {person: {name: "Alpha", age: "24"}}
console.log(myDest);  // Output: Object {person: {name: "Alpha", age: "24"}}
console.log(mySource.obj === myDest.obj); // Output: True

Answer 6

Understanding the concept of copying versus extending is important when dealing with primitives in JavaScript.

Copying:

When copying, each property of an object is iterated through. If the property is a primitive value, it is simply copied. If it is an object, a new object is created and a recursive copy is performed.

The following is a basic implementation of the copy function:

function copy(destination, source) {
  for (var prop in source) {
    if (typeof source[prop] === 'object') {
      var clone = {};
      copy(clone, source[prop]);
      destination[prop] = clone;
    } else {
      // copy the primitive
      destination[prop] = source[prop];
    }
  }
}

Extending:

Extending also iterates through each property of an object. If the property is a primitive value, it is copied. If it is an object, a reference to the original object is created instead of creating a new one.

function extend(destination, source) {
  for (var prop in source) {
    destination[prop] = source[prop];
  }
}

It's important to note that when performing a shallow copy, primitives are always cloned. To avoid this, you can change properties of a referenced object achieved through a shallow copy.

var mySource = {person: {'name' : 'Beta', 'age' : '24'}}
var myDest = {}
extend(myDest,mySource);
mySource.person.name = "Alpha";
console.log(mySource); // Output: Object {person: {name: "Alpha", age: "24"}}
console.log(myDest);  // Output: Object {person: {name: "Alpha", age: "24"}}
console.log(mySource.obj === myDest.obj); // Output: True

Answer 7

Answer №4

When dealing with object copies, certain factors come into play.

Check if the object points to the same memory location or not
Normal copy - Yes
Angular copy - No
Angular extend - No
Angular merge - No
Determine if inner objects point to the same memory location or not
Normal copy - Yes
Angular copy - No
Angular extend - No
Angular merge - No
Decide whether the copy retains current child objects or removes them
Normal copy - Override
Angular copy - Override
Angular extend - Keep
Angular merge - Keep

For a demonstration and examples, you can view this Plunker link.

// '=' assignment copy
console.info('assignment copy');
var mySource = {'name' : 'sakshi', 'age' : '24', 'obj' :{'key':'value'}}
var myDest = {oldObj:'old'} //old properties will be override
myDest = mySource;
mySource.name = "Beta";
console.log(mySource); // Object {name: "Beta", age: "24", obj: Object}
console.log(myDest); // Object {name: "sakshi", age: "24", obj: Object}
console.log(mySource === myDest); // true         //points to same object
console.log(mySource.obj === myDest.obj); // true //points to same object

// angular.copy()
console.info('angular copy');
var mySource = {'name' : 'sakshi', 'age' : '24', 'obj' :{'key':'value'}}
var myDest = {oldObj:'old'} //old properties will be override
angular.copy(mySource,myDest);
mySource.name = "Beta";
console.log(mySource); // Object {name: "Beta", age: "24", obj: Object}
console.log(myDest); // Object {name: &...

Answer 8

When dealing with object copies, certain factors come into play.

Check if the object points to the same memory location or not
Normal copy - Yes
Angular copy - No
Angular extend - No
Angular merge - No
Determine if inner objects point to the same memory location or not
Normal copy - Yes
Angular copy - No
Angular extend - No
Angular merge - No
Decide whether the copy retains current child objects or removes them
Normal copy - Override
Angular copy - Override
Angular extend - Keep
Angular merge - Keep

For a demonstration and examples, you can view this Plunker link.

// '=' assignment copy
console.info('assignment copy');
var mySource = {'name' : 'sakshi', 'age' : '24', 'obj' :{'key':'value'}}
var myDest = {oldObj:'old'} //old properties will be override
myDest = mySource;
mySource.name = "Beta";
console.log(mySource); // Object {name: "Beta", age: "24", obj: Object}
console.log(myDest); // Object {name: "sakshi", age: "24", obj: Object}
console.log(mySource === myDest); // true         //points to same object
console.log(mySource.obj === myDest.obj); // true //points to same object

// angular.copy()
console.info('angular copy');
var mySource = {'name' : 'sakshi', 'age' : '24', 'obj' :{'key':'value'}}
var myDest = {oldObj:'old'} //old properties will be override
angular.copy(mySource,myDest);
mySource.name = "Beta";
console.log(mySource); // Object {name: "Beta", age: "24", obj: Object}
console.log(myDest); // Object {name: &...

AngularJS: comparing the differences between copying and extending

Answer №1

Answer №2

Answer №3

Answer №4

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