JavaScript/JScript: Control Structures I - Pearson Learning Solutions

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Chapter 14 JavaScript/JScript: Control Structures I 405
prints Passed if the student’s grade is greater than or equal to 60 and prints Failed if the
student’s grade is less than 60. In either case, after printing occurs, the next pseudocode
statement in sequence (the next statement after the whole if/else structure) is “performed.”
Note that the body of the else is also indented.
Good Programming Practice 14.2
Indent both body statements of an if/else structure. 14.2
The indentation convention you choose should be carefully applied throughout your
programs (both in pseudocode and in JavaScript). It is difficult to read programs that do not
use uniform spacing conventions.
The preceding pseudocode if/else structure may be written in JavaScript as
if ( studentGrade >= 60 )
document.writeln( "Passed" );
else
document.writeln( "Failed" );
The flowchart of Fig. 14.4 nicely illustrates the flow of control in the if/else structure.
Once again, note that the only symbols in the flowchart (besides small circles and
arrows) are rectangles (for actions) and a diamond (for a decision). We continue to emphasize
this action/decision model of computing. Imagine again a deep bin containing as many
empty double-selection structures as might be needed to build a JavaScript algorithm. The
programmer’s job is to assemble the selection structures (by stacking and nesting) with
other control structures required by the algorithm and to fill in the empty rectangles and
empty diamonds with actions and decisions appropriate to the algorithm being implemented.
JavaScript provides an operator called the conditional operator (?:) that is closely
related to the if/else structure. The operator ?: is JavaScript’s only ternary operator—
it takes three operands. The operands together with the ?: form a conditional expression.
The first operand is a boolean expression, the second is the value for the conditional expression
if the condition evaluates to true and the third is the value for the conditional expression
if the condition evaluates to false. For example, the statement
print “Failed”
false
grade >= 60
true
Fig. 14.4 Flowcharting the double-selection if/else structure.
print “Passed”
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