1 2 3 | var x, y; // How to declare variables x = 5; y = 6; // How to assign values z = x + y; // How to compute values |
JavaScript Keywords
JavaScript keywords are some reserved words that can’t be used as identifier and are used to identify actions to be performed e.g., the var keyword tells the browser to declare variables in JavaScript.
Here is the list of JavaScript keywords:
abstract | arguments | await | boolean |
break | byte | case | catch |
char | class | const | continue |
debugger | default | delete | do |
double | else | enum | eval |
export | extends | false | final |
finally | float | for | function |
goto | if | implements | import |
in | instanceof | int | interface |
let | long | native | new |
null | package | private | protected |
public | return | short | static |
super | switch | synchronized | this |
throw | throws | transient | true |
try | typeof | var | void |
volatile | while | with | yield |
Whitespace and Line Breaks in JavaScript
JavaScript ignores spaces, tabs, and newline characters that appear in JavaScript programs.
Spaces, tabs, and newlines can be used freely.
This allows you to format and indent the programs in a neat and consistent way that increases readability.
Optional Semicolons in JavaScript
Generally the statements in JavaScript are followed by a semicolon.
However, JavaScript also allows you to omit this semicolon if each of the statements is placed on a separate line.
For example, the following code snippet can be written without semicolons:
1 2 3 4 | <script language="JavaScript" type="text/JavaScript"> variable1 = 100 variable2 = 200 </script> |
But when written in a single line as follows, semicolons must be used
1 2 3 | <script language="JavaScript" type="text/JavaScript"> variable1 = 100;variable2 = 200 </script> |
Case Sensitivity
JavaScript is case-sensitive which means that the JavaScript keywords, variables, function names, and any other identifiers must always be typed maintaining a consistent capitalization of letters.
So the identifiers DATE, date and Date will convey different meanings in JavaScript.
Comments in JavaScript
- Anything written between a // and the end of a line is treated as a comment and is not executed by JavaScript.
- Any text between the characters /* and */ is treated as a multiple line comment.
- JavaScript recognizes the HTML comment opening <!–. JavaScript treats this as a single-line comment, just like the // comment.
- The HTML comment closing sequence –> is not considered as a comment by JavaScript so it must be written as //–>.