17. What is the reason to choose the name let as a keyword?

The keyword let was introduced in ES6 (ECMAScript 2015) as a way to declare block-scoped variables in JavaScript. The choice of the name "let" comes from its historical use in programming languages and mathematical notation. Here are some reasons why "let" was chosen:

1. Inspired by Mathematics:

   • In mathematics and formal logic, "let" is commonly used to define variables. For example: $$\text{Let } x = 5$$
   • This makes let intuitive for programmers familiar with mathematical notation.

2. Used in Other Programming Languages:

   • Many programming languages, such as Scheme, Pascal, and ML, use let to define local variables.
   • Since JavaScript was influenced by multiple languages, adopting let aligned with existing conventions.

3. Semantic Meaning:

   • The word "let" implies introducing a variable for temporary use. This aligns with its behavior of defining variables within a block scope.

4. Differentiation from var:

   • JavaScript initially had only var, which is function-scoped and led to issues like accidental redeclarations and hoisting surprises.
   • let was introduced to provide block scoping and prevent such issues, making it a more reliable choice for variable declaration.

5. Avoiding Confusion with const:

   • Another new keyword, const, was introduced alongside let. Using let helps distinguish variables that can be reassigned from constants.

Summary:

The choice of let in JavaScript was influenced by mathematical notation, its use in other languages, and its semantic clarity in defining variables with block scope.