Reading Notes
Comparison operators can compare one value in the script to its expected value and result boolean
== Is Equal To compares two values (numbers, strings, or booleans) to see if they are the same
'ABC' == 'DEF' returns false'ABC' == 'ABC' returns true!= Is Not Equal To compares two values to see if they are not equal
'abc' != 'def' returns true'abc' != 'abc' returns false=== Strict Equal To compares two values to see if both their value and data type are the same
'3' === 3 returns false not same data type'3' === '3' returns true!== Strict Not Equal To compares two value to confirm that both the data type and value are not the same
'3' !== 3 returns true not the same data type or value'3' !== '3' returns false same data type and value> Greater Than checks to see if the number on the left is greater than the one on the right
4 > 3 returns true3 > 4 returns false< Less Than checks to see if the number on the left is less than the one on the right
4 < 3 returns false3 < 4 returns true>= Greater Than or Equal TO checks if the number on the left is greater than or equal to the number on the right
4 >= 3 returns true3 >= 4 returns false3 >= 3 returns true<= Less Than or Equal TO checks if the number on the left is less than or equal to the number on the right
4 <= 3 returns false3 <= 4 returns true3 <= 3 returns trueLogical Operators
&& Logical And tests more than one condition
((5 < 2) && (2 >= 3)) returns false|| Logical Or tests for at least one condition being true
((5 < 2) || (2 >= 3)) returns false((5 < 2) && (2 <= 3)) returns true! Logical Not inverts a single boolean value
!(2 < 1) returns trueShort Circuit Evaluation logical evaluations evaluate from left to right and will stop as soon as they are satisfied of the result
false && anything returns false without evaluating anything because both values cannot be truetrue || anything returns true without evaluating anything at least one of the values is trueLoops check a condition, if it returns true a code block will run then will check again, if still true, code block will run again, until no longer true
For good for running a loop a specified number of times, uses a counter as a conditionWhile good for running loops that when you don't know how many times it should runDo While similar to the while loop, but will always run the statements in the curly braces at least once even if the condition evaluates to false
for (var i = 0; i < 10; i++) {
document.write(i);
}
The preceding loop will write 0123456789 to the page.
for keyword indicating a for loop(var i = 0; i < 10; i++) Condition (Counter)document.write(i); Code to execute during loopLoop Counter
var i = 0; Initialization *creates a variable and sets it to 0i < 10; Condition loop will continue to run until it reaches a specified number, may also use a variable that holds a numberi++ Update every time the loop is run it adds one to the counterWhile Loop will continue as long as the condition in the () is true
var i = 1; //set counter to 1
var msg = ' '; // message
//store 5 times table in a variable
while (i < 10) {
msg += i + ' x 5 = ' + (i * 5) + '<br />;
i++;
}
document.getElementByID('answer').innerHTML = msg;
Loop returns the following:
1 x 5 = 5
2 x 5 = 10
3 x 5 = 15
4 x 5 = 20
5 x 5 = 25
6 x 5 = 30
7 x 5 = 35
8 x 5 = 40
9 x 5 = 45