Tutorial 4
Decision Making with Control
Structures and Statements
Section A - Decision Making
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Tutorial 4A Topics
• Section A - Decision Making
–
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–
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if statements
if…else statements
Nested if statements
switch statements
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Tutorial 4 -Decision Making with Control Structures and Statements
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Decision Making
• Decision Making
– Process of determining the order in which
statements execute in a program
• AKA – flow control
– Decision-Making Structures
• Special type of JavaScript statements used for
making decisions
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Tutorial 4 -Decision Making with Control Structures and Statements
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Decision Making
• if Statements
– Used to execute specific programming code if the
evaluation of a conditional expression returns a
value of true
• “Do this or don’t do this”
– Syntax (3 primary parts)
if (conditional_expression) {
statement(s);
}
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Decision Making
• if Statements
– Operation
• If the conditional expression is true, the
statement(s) is/are executed
• Control then continues to subsequent code
– Command block
• Multiple statements contained within a set of
braces (require curly braces)
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Decision Making
• if Statements
– Conditional Expression
• Can consist of:
– Comparison operators
– Logical operators
– Combination of the two
• Must resolve to Boolean value
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Decision Making
• if…else Statements
– Used to execute one set of code if the evaluation of
a conditional expression returns a value of true,
otherwise executes another set of code
• “Do this or do something else”
– Syntax
if (conditional_expression) {
statement(s);
} else {
statement(s);
}
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Decision Making
• Nested if and if…else Statements
– Nested statements
• Statements contained within other statements
– Syntax (variable)
if (conditional_expression) {
statement(s);
if (conditional_expression) {
statement(s);
}
} else {
statement(s);
}
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Decision Making
• switch Statements
– Controls program flow by executing a specific set of
statements, depending on the value of an
expression
– Syntax
switch (expression) {
case label1:
statement(s);
break;
case label2:
statement(s);
break;
default:
statement(s);
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}
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Decision Making
• switch Statements
– Case labels
• Identify specific code segments
• Can use a variety of data types as case labels
– Break statement
• Used to exit switch statements
– Default label
• Contains statements that execute when the condition
expression doesn’t match any of the case labels
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