Identifiers: Identifiers are nothing but the names which is given to the members of any class like a variable, method name, class name, array name etc. Certain rules to be followed while declaring Identifiers:
- Identifier name can start with both upper-case as well as lower case letter but can’t start with numbers.
- Only _ and $ symbols can be used for giving name to Identifiers, apart from these symbols, no other special symbol can be used.
- Keywords are different from Identifiers.
- Identifier are case sensitive and doesn’t contain spaces.
Examples of Valid and Invalid Identifiers:
| Valid | Invalid |
|---|---|
| geeksforgeeks | 1$geeksforgeeks |
| geeks_for_geeks | #geeks |
| $geeks | geeks-for-geeks |
| _geeks$ | any |
Keywords: Keywords are words which are responsible to perform some specific task or the words which represent some specific functionality. The following table lists some keywords:
| break | as | any | switch | case | if |
| throw | else | var | number | string | get |
| module | type | instanceof | typeof | public | private |
Comments: Comments are a way to improve the readability of a program. While coding we use comments for a better understanding of code for other users. While execution of the code, compiler ignore the comments and compile the rest of the code. There are two ways to use comments :
- Single-line comments ( // )
- Multi-line comments (/* */)
Examples: