Conclusion

Basically, there are two reasons to use var:

• Your code will be clearer. When you use var, you intentions are clear. If you are using it, you are declaring a new variable that is scoped to the current execution context (local inside a function, or global). And if in the same code there are places where you do not use var, it is clear that you are not declaring a new variable but overriding a previoulsy declared variable.
• You code will be less buggy. Using var for every variable declaration guarantees that the variable is scoped to the correct execution context. So if you happen to have variables with the same name, they will not overwrite each other. And it will force you to create all global variables outside of functions, which is a good coding practice. All global variables should be declared at the top of your program before any functions.


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