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id	title	challengeType	forumTopicId	dashedName
598f48a36c8c40764b4e52b3	Prevent Object Mutation	1	301207	prevent-object-mutation

--description--

As seen in the previous challenge, const declaration alone doesn't really protect your data from mutation. To ensure your data doesn't change, JavaScript provides a function Object.freeze to prevent data mutation.

Any attempt at changing the object will be rejected, with an error thrown if the script is running in strict mode.

let obj = {
  name:"FreeCodeCamp",
  review:"Awesome"
};
Object.freeze(obj);
obj.review = "bad";
obj.newProp = "Test";
console.log(obj);

The obj.review and obj.newProp assignments will result in errors, because our editor runs in strict mode by default, and the console will display the value { name: "FreeCodeCamp", review: "Awesome" }.

--instructions--

In this challenge you are going to use Object.freeze to prevent mathematical constants from changing. You need to freeze the MATH_CONSTANTS object so that no one is able to alter the value of PI, add, or delete properties.

--hints--

You should not replace the const keyword.

(getUserInput) => assert(getUserInput('index').match(/const/g));

MATH_CONSTANTS should be a constant variable (by using const).

(getUserInput) =>
  assert(getUserInput('index').match(/const\s+MATH_CONSTANTS/g));

You should not change the original declaration of MATH_CONSTANTS.

(getUserInput) =>
  assert(
    getUserInput('index').match(
      /const\s+MATH_CONSTANTS\s+=\s+{\s+PI:\s+3.14\s+};/g
    )
  );

PI should equal 3.14.

assert(PI === 3.14);

--seed--

--seed-contents--

function freezeObj() {
  const MATH_CONSTANTS = {
    PI: 3.14
  };
  // Only change code below this line


  // Only change code above this line
  try {
    MATH_CONSTANTS.PI = 99;
  } catch(ex) {
    console.log(ex);
  }
  return MATH_CONSTANTS.PI;
}
const PI = freezeObj();

--solutions--

function freezeObj() {
  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();

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