One of the key principles in modern JavaScript is the principle of least surprise. A major benefit of using const for non-parameter variables is the clarity it provides. Unlike let or var, when you see a const variable, you immediately know what to expect its value to be without needing to analyze the entire function. This makes the code easier to understand and reduces mental burden. Personally, I advocate for avoiding let or var in most cases.
However, when it comes to parameters, the issue of reassignability is not as clear. While it's uncommon to reassign parameters due to the confusion it can cause, especially in longer functions where code visibility is limited, there is still a risk of inadvertently changing a parameter's value. This can lead to difficult debugging scenarios, such as encountering errors related to parameters that seemingly have the correct type.
By using const for variable declarations involving parameters, such as creating a new variable like totalPrice, the code becomes much more explicit and easier to follow. This approach highlights the need to carefully assess all parameters involved in a particular calculation, reducing the chances of overlooking potential issues.
It is instances like these that demonstrate the importance of clear and consistent coding practices to avoid confusion and improve code quality.