As was explained earlier, computers are built on top of binary numbers. Two possible states are ideal for boolean logic. Boolean logic lets you determine if something is true or false. We can assign the results of a boolean expression to a variable. The mathematical conditional operators are slightly different in JavaScript due to standard keyboards not having the symbols.
Description  Math  JavaScript  Description  Math  JavaScript  

equals  =  ==  not equals  ≠  !=  
strict equals  =  ===  strict not equals  ≠  !==  
less than  <  <  less than or equals  ≤  <=  
less than  <  <  less than or equals  ≤  <=  
greater than  >  >  greater than or equals  ≥  >=  
boolean AND  ∧  &&  boolean OR  ∨    
NOT  ¬  ! 
You will notice that there are two different versions of equals in JavaScript. The double equal sign version will convert the two operands to the same type and then do the comparison. The triple equal sign was added to enforce types so that the data type must be the same for the comparison to work. As it turns out, due to some of the quirks of JavaScript’s type conversions, most programmers will use the triple equal sign version to avoid hardtofind bugs. You can simply have a variable and assign it the results of the conditional. For example:
The AND and OR operators are for combining several boolean conditions together. As can be seen by the table below, AND is true only if both conditions are true while OR is true if either or both conditions are true.
first boolean 
second boolean 
&& AND 
 OR 
!(a&&b) NAND 
!(ab) NOR 
XOR 


False  False  False  False  True  True  False  
False  True  False  True  True  False  True  
True  False  False  True  True  False  True  
True  True  True  True  False  False  False 
For example, lets say you wanted to make sure the number given was between 1 and 10. In math we could write this as 1 ≤ x ≤ 10, but JavaScript comparisons only allow one comparison, so to do the same in JavaScript you would do the following:
This checks that the number is greater than or equal to the starting value of the range and that it is also less than or equal to the upper range limit. If either of these checks fail, then the number is not in our desired range. This is why we use the AND (&&) operator. If we wanted to check if the value was outside the range, we would want to use the OR () operator as the result would have to be either less than the starting range or greater than the ending range. This would be as follows:
This is all great but what if we want a value other than true or false for your result?
You already know about unary and binary operations. Unary means you are dealing with a single component (x). Binary operations mean there are two parts (x + y). JavaScript also has something called a Ternary operator. Ternary means there are three positions in the operation. There is only one such operation in Java, and it is used as a mathematical shortcut for converting a boolean expression into another value other than a binary.
For example, say we have a boolean variable named isLeapYear and wanted to know the number of days in February, we could simply use:
Example, if strength is higher than 18 then cap it at 18:
Example If value is negative, add 10 to it.
Make sure a value is positive:
We can have the conditions return a string result as well. Return words true or false based on if b is true or false:
Return string stating if a leap year:
Return message stating if strength value is valid:
Ternary operators can be nested by having a ternary operator as the true or false result of another ternary operator. For example, if we wanted to clamp a value to be between 0 and 100 we could simply do the following:
You can chain together nested trinary operators. For example, say you wanted to print day of the week (0 = Sunday … 6 = Saturday), then you could do something like:
While getting values conditionally is great, what if we wanted to perform different actions based on the result of the condition? We will explore conditions in the next chapter.
A quick summary of the basics of JavaScript.
A brief look at how JavaScript was written in 10 days.
Comments. Why programmers don't write them, and how they should be written
Variables are used to store the state of a program.
Bits, Bytes, and data types.
Math on the computer similar but some symbol differences.
Various math operations can be used through the Math class.
Strings are what we call blocks of text and are used extensively.
Determining if a conditional expression is true or false
Conditional code using the if statement.
If statements can contain other if statements, this is called nesting.
Switch statements are a way of replacing large number of else if statements.
Functions let you put common code into a named function that can be called anywhere.
Loops allow you to repeat sections of code until conditions are met.
Just like conditional statements, loops can be nested but this has some special considerations.
Scripting languages give us the ability to dynamically change the web page.
Reacting to the user actions is done by handling events.
Coming June 23^{rd}, 2024
Coming June 30^{th}, 2024