Why can't I declare multiple const in JavaScript?

A normal variable (declared with var or let) can be declared without a value, since you can assign to them later:

let foo;  // foo has value undefined
foo = 3;  // foo has value 3

However, you can't do the same with constants since you can't change their value after they have been declared:

const foo;  // ...?
foo = 3;    // this is not allowed because foo is constant

Therefore, you must declare and assign a value to a constant at the same time. This can be done with multiple consts at once:

const foo = 3,
      bar = 8; // this works fine, foo and bar are both constants

There's no way to declare a const in one spot and assign it in another. You must use var or let instead.

As Sean Sobey said in his answer, this is because const values have to be declared with values.

I would add that you can declare multiple const values in one statement, e.g.

const [xMin, xMax, yMin, yMax] = [-2, 2, -1.5, 1.5];

It is useful to note (contrary to other answers here) that a const is not immutable. See: https://softwareengineering.stackexchange.com/questions/149555/difference-between-immutable-and-const

For example:

const item = { price: 10 };
item.price= 15;
console.log(item.price);

This will output the updated price of 15.

You can, but is a constant so you have to assign them a value in declaration

const values cannot be changed after assigning. You are trying to declare it now to change its later, which is not going to work with const. The solution of this problem is that you declare it with let or var.

I would declare multiple variables like this:

const latCoordinate = 12, longCoordinate = 34

Or you could also do something like that if you have an Object in the first place:

const {latCoord, longCoord} = {latCoord: -0.12768, longCoord: 51.50354}

In that case, you can name variables the way you want like so:

const {latCoord: lat, longCoord: lng} = {latCoord: -0.12768, longCoord: 51.50354}
console.log(lat, lng) // => -0.12768, 51.50354

const should be assigned a value when it's declared since it makes a read-only.