What does the 'let' keyword do in JavaScript?

The 'let' keyword in JavaScript is used to declare a block-scoped variable that can be re-assigned. This means that once a variable is declared using let, it can be updated or modified with a new value later on. Unlike variables declared with the 'var' keyword, which are function-scoped or globally scoped, the scope of a variable declared with 'let' is limited to the block in which it is defined, making it a more predictable choice for managing variable scope.

This behavior allows developers to create variables that are intended to be changed after their initial assignment, providing flexibility while coding. For instance, inside a loop or a conditional statement, using 'let' allows the variables to retain their values specific to that block and prevents unintended leakage of that variable into the containing scope.

In contrast, declaring a constant variable is the realm of the 'const' keyword, which prevents re-assignment after its initial assignment. Defining a function is done using the 'function' keyword or function expressions, and initializing an object typically involves object literal syntax or constructor functions, rather than 'let'. Therefore, the core function of 'let' is centered around the declaration of variables that are mutable and have a block-level scope.