Why do you create your variables at the top of your program?
Creating a variable and updating a variable is put on the top to allow for a call back to the variable in the program. Variables allow for changes in the program and are important for this reason.
Do you declare variables in main?
Local variables are declared inside the braces of any user defined function, main function, loops or any control statements(if, if-else etc) and have their scope limited inside those braces.
Should you declare all variables at top?
In JavaScript, one should declare all variables at the beginning of the function to mitigate the risk of mistakes related to the fact that the scope of variables is a function.
Why do we declare variables?
Before they are used, all variables have to be declared. Declaring a variable means defining its type, and optionally, setting an initial value (initializing the variable). Variables will roll over when the value stored exceeds the space assigned to store it. See below for an example.
How do you declare and use variables?
To declare (create) a variable, you will specify the type, leave at least one space, then the name for the variable and end the line with a semicolon ( ; ). Java uses the keyword int for integer, double for a floating point number (a double precision number), and boolean for a Boolean value (true or false).
Is it bad to declare variables at the top of a function?
Variables should be declared as locally as possible. Declaring variables “at the top of the function” is always a disastrously bad practice.
Why do I declare variables close to where they are used?
Now there are very good reasons to declare variables close to where they are used: Makes it easy to determine the type, when reading code. Makes it easy to delete code including the declaration all together. But as you suggest, for some languages there are better reasons to not do that, for sake of clarity or scope.
When to declare variables in a JavaScript function?
In JavaScript, one should declare all variables at the beginning of the function to mitigate the risk of mistakes related to the fact that the scope of variables is a function. The following code illustrates this non-intuitive scope by actually printing “Hello, World” to the console:
When to declare a variable at the top of a method?
Also, if a method is long enough that having the variable declaration at the top means it isn’t close to it’s use then it could probably benefit from refactoring into separate methods. Doing this will also help readability because you’ll have method names explaining what’s happening. Some examples (quotes as this is only my opinion):