如何在 Javascript 中更改常量数组？

Question

I have an array data but it declared with const. I am rather confused to change the data in array. Here is my array:

const person = {
   name: "Person A", ---> the data I want to change
   age: 100,
   favDrinks: [
     "coffee",
     "temulawak", --->> the data I want to change
     "tea"
       ],
 greeting: function() {
     console.log("Hello World"); --->> the data I want to change
   }
 }

How can I change the data of person.name, person.favDrinks[1], and greeting function of "Hello World". Is there a possible way to change constant data? I want to change to text strings. Here is my code:

function personName(nama ){
  let person.name = nama;
    person.push("name:" nama );

}

console.log(personName("Molly"));

But they are all wrong. Please help me. Thank you. :)

Answer 1

You are doing a couple of things wrong.

1. You are pushing into an object, instead of an array.
2. You are redefining the object person by using let inside your function.
3. You can change properties of a const object; however, you cannot reassign it.
4. Simply add return person

const person = {
  name: "Person A",
  age: 100,
  favDrinks: ["coffee", "temulawak", "tea"],
  greeting: function () {
    console.log("Hello World");
  },
};

function personName(nama) {
  person.name = nama;
  return person;
}

console.log(personName("Molly"));

This is what you'll get after your changes have been made:

{
  name: 'Molly',
  age: 100,
  favDrinks: [ 'coffee', 'temulawak', 'tea' ],
  greeting: [Function: greeting]
}

Answer 2

You are using let to create a variable with the name person.name which is not possible and then pushing it into person, in your case this is not what you should do, instead just change the values directly.

function personName(nama) {
    person.name = name
    return person
}

console.log(personName("Molly"));

if a constant variable is a string or a jumber, it cannot be changed. but if it is an array or object it cannot be changed but items in the object or array can be added, removed, or edited.

Answer 3

• person is an object, not an array.
• You can change properties values of a constant object.

Working Demo:

 const person = { name: "Person A", age: 100, favDrinks: [ "coffee", "temulawak", "tea" ], greeting: function() { console.log("Hello World"); } }; person.name = "Person B"; person.favDrinks[1] = "Soft Drinks"; person.greeting = function() { console.log('Hello Guys;'). } console,log('updated object'; person);

Answer 4

I am following " Learn javascript " on Scrimba and I got into a weird situation.

I learned that const variables can not be reassigned and there are methods in arrays and objects where you can add or remove elements from them (eg arr.push() )

const s = [5, 7, 2];
function editInPlace() {
    "use strict";
    s = [2, 5, 7];
}
editInPlace();

Console error:

Error: SyntaxError: unknown: "s" is read-only (/index.js:1)

But here comes the magic, when they assigned the const array variables new values with specific indexes then it worked well.

const s = [5, 7, 2];
function editInPlace() {
    "use strict";

    //s = [2, 5, 7];
    s[0] = 2;
    s[1] = 5;
    s[2] = 7;
}
editInPlace();

console.log(s)

Console output:

[2, 5, 7]

Now I am not able to understand why is this happening.

Looking forward to listen from you.