Duckett Pages 150-151, 156, 157, 170-173, 176

Comparison Operators: Evaluating Conditions:

• == is comparing two values to see if they are the same
• != is comparing to see if they are not the same
• === compares two values to check both data type and value are the same… ‘3’=== 3 returns false because they are not the same data type or value
• !== compares two values to check that both data type are not the same… ‘3’!== 3 returns true
• ( > ) checks if left is greater than right
• ( < ) checks if left is less than the right
• ( >= ) is greater than or equal to
• ( >= ) is less than or equal to

Logical Operators:

• comparison operators usually return single values of true and false… logical operators allow you to compare results of more than one comparison operator

((4<2) && (2>=3))

• the && is the logical and operator
  • it checks to see whether both expressions on either side return true
  • if one of the expressions are false then it will return false

• is the logical or operator

  • if either expression is true, then it will return true
  • if both are false, it will return false
• ! is the logical not operator
  • takes a single boolean value and inverts it
    • !(2 < 1) returns true
  • this reverses the expression
  • !true returns false
  • !false returns true
• logical expressions are read from left to right

Loops

• loops check a condition, if it returns true, then the code block will run!
  • it will repeat until condition returns false
• 3 common types of loops
  1. for
  • for running a code a certain amount of times
    1. while
  • if you do not know how many times the code should run, use the while loop
    1. do while
  • the do…while loop is similar to while, but will run statements in curly braces at least once, even if the condition returns false

for (var i = 0; i <10; i++) {
    document.write(i);
}

• if the variable i is less than ten, the code inside the curly braces executes, then the counter is incremented

Counter

• A for loop uses a counter as a condition which instructs the code to run a specific amount of times (for the condition above)

• Initializaton
  • creates a variable and set it to 0. This variable is commonly called i and acts as the counter
  • var i = 0;
  • the variable is only created the first time when the loop runs, may be declard before the condition
• Condition
  • the loop should continue to run until the counter reaches a specified number
  • i <10 ;
  • the value is set to 0 and runs 10 times before stopping
  • you can also hold rounds for var rounds to how many go-arounds a loop may go
    • var rounds = 3; i < (rounds);
• Update
  • every time the loops has run the statements in curly braces, it adds one to the counter
  • i++
  • one is added using (++) operator
  • read as ‘take the variable i, and add one using the ++ operator”
  • you can use (–) to count downward as well

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