NOTE: be aware that the accepted response has a link to an obsolete Google style guide
This is nice (string literals or integer literals):
const PI = 3.14;
const ADDRESS = '10.0.0.1';
but…
const myObject = { key: 'value' };
const userSuppliedNumber = getInputNumber()
Google JavaScript Style Guide says:
Declare all local variables with either const or let. Use const by
default, unless a variable needs to be reassigned. The var keyword
must not be used.Every constant is a @const static property or a module-local const
declaration, but not all @const static properties and module-local
consts are constants. Before choosing constant case, consider whether
the field really feels like a deeply immutable constant. For example,
if any of that instance’s observable state can change, it is almost
certainly not a constant. Merely intending to never mutate the object
is generally not enough.
JavaScript.info says:
…capital-named constants are only used as aliases for “hard-coded”
values.