What does `const` ensure when declaring a variable?

When using const to declare a variable in JavaScript, it signifies that the variable must be initialized when it is declared and that it cannot be re-assigned to a different value afterward. However, it is essential to clarify that while the variable itself cannot be assigned a new value, if it refers to an object or an array, the contents of that object or array can still be modified.

In other words, const helps prevent accidental variable re-assignment, promoting more predictable and maintainable code. This characteristic is particularly beneficial in a codebase where accidental changes to variable bindings can lead to errors that are hard to trace.

For instance:

const myArray = [1, 2, 3];
myArray.push(4); // This is allowed – the contents of the array can change.
myArray = [5, 6, 7]; // This will throw an error – re-assignment is not allowed.

This illustrates the nature of const, where the variable's reference cannot change, but the value itself, if it is an object or an array, can be altered. Thus, the correct response emphasizes the inability to re-assign the variable itself while allowing the mutation of the