Encapsulation in JavaScript

JavaScript does not allow you to define a method as public or private. This is a limitation users need to get around to, because in real life you don't want to expose all methods as public method.

Here is a simple implementation of the case where you want to verify input code.

function verifycode(code) {
  console.log(code.length);
  return code.length == 4 ? true : false;
}

function info(code) {
  if (verifycode(code)) {
    console.log(code + " is valid");
  } else {
    console.log(code + " is wrong");
  }
}

info("abcd");
info("rty");

In the above implementation anyone can call the method verifycode. Not good. Here is one way to fix this problem.

var Lab = Lab || {};
Lab = (function () {
  var verifycode = function (code) {
    console.log(code.length);
    return code.length == 4 ? true : false;
  };
  return {
    info: function (code) {
      if (verifycode(code)) {
        console.log(code + " is valid");
      } else {
        console.log(code + " is wrong");
      }
    },
  };
})();

Lab.info("abcd");
Lab.info("rty");
Lab.verifycode("abcd"); //verifycode is private

Another way to solve the same problem would be to create a constructor function. Here is an implementation.

function Lab(code) {
  this.code = code;
  var verifycode = function () {
    return code.length == 4 ? true : false;
  };
  this.info = function () {
    if (verifycode()) {
      console.log(code + " is valid");
    } else {
      console.log(code + " is wrong");
    }
  };
}
new Lab("abcd").info();

Here is another way to solve the same problem. In this case I have moved all the public methods to prototype.

function Lab(code) {
  this.code = code;
  this.verifycode = function () {
    l = code.length;
    return l == 4 ? true : false;
  };
}

Lab.prototype.info = function () {
  if (this.verifycode()) {
    console.log(this.code + " is valid");
  } else {
    console.log(this.code + " is wrong");
  }
};

new Lab("abcd").info();