JavaScript constructor function is a special method used to create and initialize an object instance. Use the new keyword to create an object from a constructor function.
constructor() { /* ... */ }
constructor(argument0) { /* ... */ }
constructor(argument0, argument1) { /* ... */ }
constructor(argument0, argument1, ... , argumentN) { /* ... */ }Recommended naming constructor functions with an upper-case first letter.
JavaScript constructor function
Simple example code of object constructor function.
<!DOCTYPE html>
<html>
<body>
<script>
// constructor function
function Person () {
this.name = 'John',
this.age = 23
}
// create an object
const p1 = new Person();
p1.name = "Mike"
p1.age = "100"
console.log(Person)
console.log(p1)
</script>
</body>
</html> Output:
Create Multiple Objects with Constructor Function
// create objects
const p1= new Person();
const p2= new Person();JavaScript this Keyword
The this keyword is used in a constructor function,where it refers to the object when the object is created.
// constructor function
function Person () {
this.name = 'John',
}
// create object
const person1 = new Person();
// access properties
console.log(person1.name); // JohnConstructor Function Parameters
You can also create a constructor function with parameters.
Adding a Property to a Constructor
Person.nationality = “English”;
To add a new property to a constructor, you must add it to the constructor function:
function Person(first, age) {
this.firstName = "AAA";
this.age = 25;
this.nationality = "XYZ";
}Adding a Method to a Constructor
Constructor function can also define methods:
function Person(first, age) {
this.firstName = "AAA";
this.age = 25;
this.nationality = "XYZ";
this.name = function() {
return this.firstName;
};
}Built-in JavaScript Constructors
new String() // A new String object
new Number() // A new Number object
new Boolean() // A new Boolean object
new Object() // A new Object object
new Array() // A new Array object
new RegExp() // A new RegExp object
new Function() // A new Function object
new Date() // A new Date object Do comment if you have any doubts or suggestions on this Js constructor topic.
Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.
OS: Windows 10
Code: HTML 5 Version
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