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Using Constants with Arrays and Objects
2:44Using constants prevents values from being reassigned but how do they work with arrays and objects?
We've seen that you cannot reassign a
constant variable in the case of a number
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or a string.
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The same goes for
any value of a constant variable.
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You cannot reassign strings, numbers,
booleans, objects, and arrays.
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Unlike strings, numbers, and booleans,
objects in arrays have methods and
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properties that modify the objects or
array.
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Do they still work with const?
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First we'll declare a variable,
which is a constant called days.
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This will contain an array
with a single string "Monday".
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Second we'll declare
another constant variable
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person that contains an object
literal with a {first_name}.
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Key, with the string "Imogen".
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Let's attempt to modify these
in the console here, first days.
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Let's use the push method to
add another day to the array.
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It didn't error, it returned the number 2,
meaning the new array length.
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If we type days, and hit Enter,
we get Monday and Tuesday returned.
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Let's try and add a last_name
property to the person object.
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Again no error.
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When we type person and
hit Enter we get an object
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literal back with the first_name and
last_name properties.
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So what's happening here?
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Const doesn't prevent complex objects like
arrays and objects from being modified.
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It just prevents them from being
reassigned or over written completely.
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For example, when I attempt to override
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person with another object literal.
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It shows an error, because I'm attempting
to re-assign person with a new object.
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However, if I modified the first name.
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To equal another value,
Andrew, I don't get any errors.
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