如何在 Javascript 中实现封装

Question

I am fairly new to Javascript and I was reading the docs and,

According to MDN Docs:-

Keeping an object's internal state private , and generally making a clear division between its public interface and its private internal state, is called encapsulation.

They have not mentioned

How to keep an Object's Internal State Private?

Also its mentioned further that,

In languages that don't enforce access like this, programmers use naming conventions, such as starting the name with an underscore, to indicate that the property should be considered private.

So what does this line mean

starting the name with an underscore, to indicate that the property should be considered private.

Does this mean if I put _ before a property name it would become private, isn't there a difference between becoming private and making private. Does putting an underscore tells Javascript explicitly that this property is private?

Also they have not provided any concrete code to explain that part I could only find the pseudocode

class Student : extends Person
    properties
       year
    constructor
        Student(name, year)
    methods
       introduceSelf()
       canStudyArchery() { return this.year > 1 }

I googled this and found that closures are used to implement encapsulation behaviour, but the MDN Docs have not stated this anywhere Object-oriented_programming#encapsulation

Question:- How to implement encapsulation in Javascript without closure can we use something like Object.freeze can someone explain with an example

Thank You.

Answer 1

Does this mean if I put _ before a property name it would become private

No. _ before a field name is used to convey to the reader that these field(s) are meant to be private; technically they are not private. Other code can access them and mutate them.

Fields that are truly private were recently introduced in the Javascript language.

Before the above mentioned feature was introduced, Javascript devs used different techniques to implement private fields - using closures was one of them.