The “const” keyword in JavaScript is used to create constants, variables that can't change. Curiously, though, we do seem to be able to edit objects and arrays that are created using “const”. In this tutorial, we're going to dig into the incredibly-important distinction between “assignment” and “mutation” in JavaScript.

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Josh W Comeau

The keyword in JavaScript is used to declare a constant. This is a core concept in JavaScript, and so many things make more sense when you have a clear understanding of this distinction. When we create a constant with, we can be 100% sure that the variable will never be re-assigned, but no promises are made when it comes to mutation.

The “const” Deception

Link to this heading Variable names as labels

Link to this heading Reassigning our labels

Link to this heading Primitive data types

Link to this heading Additional resources