How to define a private method or variable inside a class in JavaScript or ES6
1. With ES6 classes
Read-only “power” property example:-
For power property, let’s make it read-only, It sometimes happens that a property must be set at creation time only, and then never modified.That’s exactly the case for a coffee machine, power never changes.
To do so, we only need to make getter, but not the setter:
2. With ES5
In above code 'marks' variable is private variable, it can be accessed using getMarks() method and can be set Using setMarks() method, but can't be accessed directly.
class CoffeeMachine {
constructor(power) {
this._power = power;
}
get power() {
return this._power;
}
}
// create the coffee machine
let coffeeMachine = new CoffeeMachine(100);
alert(`Power is: ${coffeeMachine.power}W`); // Power is: 100W
coffeeMachine.power = 25; // Error (no setter)
//In below marks is private
function Employee() {
var marks=40;
return {
getMarks:function() {
return marks;
},
setMarks:function(value) {
marks=value;
}
}
}
var test=Employee();
console.log(test.getMarks()); //40
test.setMarks(70);
console.log(test.getMarks()); //70
console.log(test.marks) // undefined