Microsoft® JScript™ Writing JScript Code | JScript Tutorial Previous Next

> Like many other programming languages, Microsoft JScript is written in text format, and is organized into statements, blocks consisting of related sets of statements, and comments. Within a statement you can use variables, immediate data such as strings and numbers, and expressions.

##### Statements

> A JScript code statement consists of one or more items and symbols on a line. A new line begins a new statement, but it is a good idea to terminate your statements explicitly. You can do this with the semicolon (;), which is the JScript termination character.

> >     aBird = "Robin";
> >     var today = new Date();

> A group of JScript statements that is surrounded by braces ({}) is called a block. Blocks of statements are used, for example, in functions and conditionals. In the following example, the first statement begins the definition of a function, which consists of a block of five statements. The last three statements, which are not surrounded by braces, are not a block and are not part of the function definition.

> >     function convert(inches)  {
> >         feet = inches / 12;  //  These five statements are in a block.
> >         miles = feet / 5280;
> >         nauticalMiles = feet / 6080;
> >         cm = inches * 2.54;
> >         meters = inches / 39.37;
> >     }
> >     km = meters / 1000;  //  These three statements are not in a block.
> >     kradius = km;
> >     mradius = miles;

##### Comments

> A single-line JScript comment begins with a pair of forward slashes (//). A multiline comment begins with a forward slash and asterisk in combination (/*), and ends with the reverse (*/).

> >     aGoodIdea = "Comment your code thoroughly.";  //  This is a single-line comment.

> >     /*
> >     This is a multiline comment that explains the preceding code statement.

> >     The statement assigns a value to the aGoodIdea variable. The value, which is contained between the quote marks, is called a literal. A literal explicitly and directly contains information; it does not refer to the information indirectly. (The quote marks are not part of the literal.)
> >     */

> >     //  This is another multiline comment, written as a series of single-line comments.
> >     //  After the statement is executed, you can refer to the content of the aGoodIdea
> >     //  variable by using its name, as in the next statement, in which a string literal is
> >     //  appended to the aGoodIdea variable by concatenation to create a new variable.

> >     var extendedIdea = aGoodIdea + " You never know when you'll have to figure out what it does.";

##### Assignments and Equality

> The equal sign (=) is used in JScript to indicate the action of assigning a value. That is, a JScript code statement could say

> >     anInteger = 3;

> It means "Assign the value 3 to the variable anInteger," or "anInteger takes the value 3." When you want to compare two values to find out whether they are equal, use a pair of equal signs (==). This is discussed in detail in Controlling Program Flow.

##### Expressions

> A JScript expression is something that a person can read as a Boolean or numeric expression. Expressions contain symbol characters like "+" rather than words like "added to". Any valid combination of values, variables, operators, and expressions constitutes an expression.

> >     var anExpression = "3 * (4 / 5)";
> >     var aSecondExpression = "Math.PI * radius * 2";
> >     var aThirdExpression = aSecondExpression + "%" + anExpression;
> >     var aFourthExpression = "(" + aSecondExpression + ") % (" + anExpression + ")";

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