Today I Learned

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Freeze An Object, Sorta

You can freeze a JavaScript object using Object.freeze which will help enforce some immutability practices. Don’t be fooled though, you can still modify arrays and objects in the frozen object.

Here is what the docs have to say:

The Object.freeze() method freezes an object: that is, prevents new properties from being added to it; prevents existing properties from being removed; and prevents existing properties, or their enumerability, configurability, or writability, from being changed, it also prevents the prototype from being changed.

And here is Object.freeze in action:

> const things = {one: "two", hello: "world", cats: ["Von Neumann", "Sosa"]}
undefined
> Object.freeze(things)
{one: "two", hello: "world", cats: Array(2)}

> things.one = "three"
"three"
> things.dogs = []
[]
> delete things.hello
false

> things
{one: "two", hello: "world", cats: Array(2)}

> things.cats.push("Sneaky")
3

> things
{one: "two", hello: "world", cats: Array(3)}

See the MDN Docs for more details.

h/t Jake Worth