$.extend() in jquery
The $.extend()
function in jQuery is a powerful utility for merging objects. It allows you to copy properties from one or more source objects to a target object. Here's a detailed breakdown of how it works:
Syntax
$.extend(target, object1, [objectN])
- target: The object that will receive the properties from the source objects.
- object1, objectN: One or more objects containing properties to be copied into the target object.
Key Points
-
Shallow Copy by Default: By default,
$.extend()
performs a shallow copy. This means that if the source objects contain nested objects, only the references to those objects are copied, not the objects themselves. -
Deep Copy Option: You can perform a deep copy by setting the first argument to
true
. This will recursively copy all properties and sub-properties. -
Order of Merging: Properties from later objects will overwrite properties from earlier objects if they have the same name.
Examples
Shallow Copy
var target = { name: 'John', age: 25 };
var source = { age: 30, city: 'New York' };
$.extend(target, source);
console.log(target);
// Output: { name: 'John', age: 30, city: 'New York' }
In this example, target
is updated with properties from source
. The age
property in target
is overwritten by the age
property from source
.
Deep Copy
var target = { name: 'John', details: { age: 25 } };
var source = { details: { age: 30, city: 'New York' } };
$.extend(true, target, source);
console.log(target);
// Output: { name: 'John', details: { age: 30, city: 'New York' } }
Here, $.extend(true, target, source)
performs a deep copy. The details
object inside target
is fully replaced with the details
object from source
.
Use Cases
- Merging Settings: Combine default settings with user-defined settings in a plugin or application.
- Object Augmentation: Add properties from multiple sources to a single object.
- Cloning Objects: Create a new object with properties copied from existing objects.
Important Considerations
- Overwriting Properties: Be aware that properties in later objects will overwrite those in earlier objects with the same name.
- Handling Nested Objects: For deep copying, ensure you use the
true
flag to avoid only copying references.
$.extend()
is versatile and can be used in various scenarios where you need to combine or modify objects in JavaScript.
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