Variable name restrictions

A variable name cannot have spaces.

A variable name cannot have dashes (-). Underscores (_) are allowed and used instead.

A variable name cannot include any punctuation characters other than the dollar sign $ and underscore (_).

A variable name cannot start with a number.

A variable name cannot be an existing keyword like const or var.

There are quite a few keywords cannot be used - return, let, class, for, if, else, etc. Most coding editors will change the color of the variable name to indicate that you are using a language keyword.

It is worth noting that despite type being a keyword in TypeScript, you can still use type as a variable name.

In general, you should use descriptive variable names that accurately describe the type of information they contain.