Cacher is the code snippet organizer for pro developers

// const
"use strict";
const s = [5, 6, 7];
s = [1, 2, 3]; // throws error, trying to assign a const
s[2] = 45; // works just as it would with an array declared with var or let
console.log(s); // returns [5, 6, 45]

// freeze関数を使用してimmutableに変更可能
let obj = {
  name:"FreeCodeCamp",
  review:"Awesome"
};
Object.freeze(obj);
obj.review = "bad"; // will be ignored. Mutation not allowed
obj.newProp = "Test"; // will be ignored. Mutation not allowed
console.log(obj); 
// { name: "FreeCodeCamp", review:"Awesome"}

// for example
function freezeObj() {
  'use strict';
  const MATH_CONSTANTS = {
    PI: 3.14
  };
  Object.freeze(MATH_CONSTANTS);

  try {
    MATH_CONSTANTS.PI = 99;
  } catch(ex) {
    console.log(ex);
  }
  return MATH_CONSTANTS.PI;
}
const PI = freezeObj();