In JavaScript - ECMAScript 2021, private methods can be defined using a new syntax called "private class fields". This syntax use the # symbol to mark a method as private.
Here is an example of how to define a class with private methods in JavaScript-ES2021:
class MyClass {
#privateMethod () {
console.log('This is a private method.')
}
publicMethod () {
console.log('This is a public method.')
// calling a private method
this.#privateMethod()
}
}
let myObj = new MyClass()
myObj.publicMethod() // Output: This is a public method. This is a private method.
myObj.#privateMethod() // Uncaught SyntaxError: Private field '#privateMethod' must be declared in an enclosing class.
In this example, MyClass is defined with a private method #privateMethod() and a public method publicMethod().
To access the private method from within the public method, we use this.#privateMethod().
However, attempting to access the private method from outside the class, such as myObj.#privateMethod(), will result in an error. This is because private methods, like other private class fields, are not accessible from outside the class they were defined in.
By using private class fields, we can ensure that our private methods remain inaccessible and unmodified from outside the class, providing a secure and encapsulated solution.