JavaScript conditional

Boolean Logic Basis for modern computer logic George Boole Basis for modern computer logic Works with only two values George Boole was an english mathematician and philosopher. Born 1815, died 1864.

BOOLEAN VARIABLE OR EXPRESSION Holds either true or false can pass as a literal Can be thought of as yes or no Open excel – type true or false into a cell, and show that excel automatically capitlizes & centers it. TRUE & FALSE are special values in excel.

Is greater than or equal to Boolean expressions Creates a Boolean value from numbers or strings Operator Meaning == Is equal to != Is not equal > Is greater than < Is less than >= Is greater than or equal to <= Is less than or equal to

Conditionals Test if a Boolean expression is true or false Allows a program to make a choice

IF … THEN … ELSE if (MUST BE LOWERCASE) no else: do nothing if not true else: one or the other else if: series of choices

More complicated IF example Let’s assign letter grades to students! 90 - 100 – A 80 - 89 – B 70 - 79 – C 60 - 69 – D <60 – F Nested If: =IF(H2>=90, “A”, If(H2 >=80, “B”, “C or Below”)) Longer Nested if: =IF(H2>=90, "A", IF(H2>=80, "B", IF(H2>=70, "C", IF(H2 >=60, "D", "Fail"))))

Decision Tree grade < 60 F grade < 70 D grade < 80 C B A

In JavaScript if (num < 60) { grade = "F"; } else if (num < 70) { grade = "D"; } else if (num < 80) { grade = "C"; } else if (num < 90) { grade = "B"; } else { grade = "A"; }

When you have more than one decision to make nested else When you have more than one decision to make

Example If you live in the United States: US? Do you live in the District of Columbia or elsewhere? If you don’t live in the United States: Do you live in Europe or elsewhere? US? no yes DC? Europe? yes no no yes DC state Europe other

In JavaScript if (where == "US") { if (US == "DC") { report = "In DC"; } else { report = "In a state"; } } else if (continent == "Europe") { report = "In Europe"; } else report = "Other continent";

Combining Boolean expressions

Operations on Booleans AND OR Are all of them true? && Is it a big dog? (size==“big” && pet==“dog”) Number between 5 and 10 (num>=5 && num<=10) Are any of them true? || Is it either blue or black? (color==“blue” || color==“black”) Number less than 10 or greater than 20 (num<10 || num>20)