Keyword ‘const’ does not make the value immutable. What does it mean?

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When you make something const in JavaScript, you can’t reassign the variable itself to reference something else. However, the variable can still reference a mutable object.

const x = {a: 123};

// This is not allowed.  This would reassign `x` itself to refer to a
// different object.
x = {b: 456};

// This, however, is allowed.  This would mutate the object `x` refers to,
// but `x` itself hasn't been reassigned to refer to something else.
x.a = 456;

In the case of primitives such as strings and numbers, const is simpler to understand, since you don’t mutate the values but instead assign a new value to the variable.

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