Page 64 - Chinmaya_C8_flipbook
P. 64

STATEMENTS IN JAVASCRIPT


                  Commands  and instructions  given to  the
                  JavaScript interpreter to take some actions
                                                                                  Subject: The confirm( ) Method
                  are called  statements and a collection  of
                                                                                  The confirm() method displays a dialog
                  statements is called a script or a program.                     box  with  a  specified  message,  along
                  Within  almost  every browser resides                           with an OK and a Cancel button.
                  the  JavaScript  interpreter.  We  use  the
                  semicolon to terminate a statement but, if
                  the statements are written in separate lines, then the semicolon can be omitted.

                  JavaScript statements consist of keywords, variables, operators, expressions and comments.
                  Let us learn about them in detail.

                  KEYWORDS

                  A keyword is a reserved word that has a special meaning for the JavaScript interpreter. Some of
                  the keywords of JavaScript are:

                                          var,  switch,  let,  for, const,  function,  if,  return, etc.

                  VARIABLES

                  A variable is the name of storage location. It stores a value that can be modified later. JavaScript
                  is a loosely typed language which means it does not require a data type to be declared before
                  using it. Syntax to declare a variable in JavaScript is:

                  var <variable name> = <value>;
                  where var is a keyword, <variable name> is a valid name for the variable and <value> is the value

                  that you want to assign to the variable.
                  For example:

                  var age = 16;
                  var name = "A"
                  We can declare multiple variables in the same line in the following way:

                  var v1 = 1, v2 = "Delhi", v3;

                  Variable Naming Conventions
                  Some of the naming conventions that need to be followed while declaring variables in JavaScript are:

                      Variable names are case-sensitive which means that the variable name 'AGE' is different from
                    'age'.

                      A variable name must not start with digits 0–9.
                      Variable names can contain letters, digits, or the symbols $ and _.
                      A variable name cannot be a reserved keyword.




                   62   Premium Edition-VIII
   59   60   61   62   63   64   65   66   67   68   69