JavaScript Lecture 2 : topics to be covered

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JavaScript Lecture 2 topics to be covered

• Assignment/ recitation topics/ late-box
• Appendices
• Review
• Assignment
• Expression
• Operators

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Visit.

• www.w3schools.com
• For JavaScript and HTML tutorials
• TA websites (TA Email list page)
• For examples of code

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Assignment statement

• ltvariablegt ltassignment symbolgt ltexpressiongt
• Eg. Area pi r r

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Expressions

• Variables
• Operators
• Arithmetic
• Relational
• Logical

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Arithmetic operators

• Symbols of basic arithmetic
• Division /
• Multiplication
• Addition
• Subtraction
• Operator precedence

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• All of the above are binary operators
• ab , ab, a/b, a-b
• a and b are known as operands
• Unary operators involve one operand
• Eg. Negate (-)
• -a, -4

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Modulus operator(mod)

• Divides the two integers and returns the
  remainder as result
• Eg. 5 2 1
• 4 2 0
• Division returns the quotient
• 4 / 2 2

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• ltScript Language"JavaScript"gt
•   var EarningsJob1, EarningsJob2 
• var TotalForTheWeek
• EarningsJob1 325.38
•   EarningsJob2 580.64
•   TotalForTheWeek EarningsJob1
  EarningsJob2
• document.write("ltpgtSalarieslt/pgt") 
• document.write("Job 1")
•   document.write(EarningsJob1)
•  
• document.write("ltbrgt") 
• document.write("Job 2 ")
•   document.write(EarningsJob2)
•  
• document.write("lthr alignleft width120
  colorFF5758gt")

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(No Transcript)
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Relational Operators

• Make comparison between two values
• Returns Boolean value - either true or false
• a lt b Is a less than b?
• a lt b Is a less than or equal to b?
• a b Is a equal to b?
• a ! b Is a not equal to b?
• a gt b Is a greater than or equal to b?
• a gt b Is a greater than b?

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• Eg.
• salary gt 1000
• age gt 18
• course cs170

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Logical Operators

• test two or more relationships together
• course cs170 and section lt8
• course cs170 and section lt7
• AND
• OR
• NOT

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Logical AND operator

• exp1 exp 2
• outcome is true if the outcome for both exp1 and
  exp2 are true
• course cs170 and section lt8
• in JavaScript ? course cs170 section lt8
• course cs170 and section lt7
• in JavaScript ? course cs170 section lt7

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Logical OR operator

• exp1 exp 2
• outcome is true if the outcome for either exp1
  and exp2 are true
• section 3 section 6

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vis-à-vis

• section gt3 section lt5
• all sections greater than 3 and less than 5
• (this shall be true only for section 4)
• section gt3 section lt5
• all sections greater than 3 or less than 5
• (this shall be true for all sections)

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Logical NOT operator

• !
• Unary operator
• !(expression)
• Outcome is the opposite of the value of
  operand
• !(section lt 3 section gt 5)
• True for 4

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..looking back

• / -
• lt lt ! gt gt
• !

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Operator Overload

• Use of an operator with different data types
• 4 5
• Outcome 9
• Overload an operator to operate on other data
  types.
• four five
• Outcome fourfive

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Example of operator overload - concatenation

• operator is overloaded
• For string operands
• Concats or joins the two string operands together
• 4 5 Outcome 9
• four five Outcome fourfive
• 4 5 Outcome 45

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• document.write (four five)
• outcome fourfive
• var name Jim
• document.write (employee name name)
• outcome employee name Jim

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• var name Jim
• document.write (employee nameltbgt name
  lt/bgt)
• outcome employee name Jim

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• lthtmlgt
• ltheadgt
• lt/headgt
• ltbodygt
• ltscript type"text/javascript"gt
• var name Jim"
• document.write(Name name)
• name Jane"
• document.write(Nameltugt"name"lt/ugt")
• document.write("ltbgt regular HTML text
  lt/bgtltbrgt")
• var i2
• document.write(i"ltbrgt")
• i105
• document.write(i)
• lt/scriptgt
• lt/bodygt

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• Name Jim
• Name Jane
• regular HTML text
• 2
• 105