Square Root

returns the square root of a number

Math.sqrt(81);

9

Powers

returns the base (first number) raised to the power (second number)

Math.pow(2,3);

8

Minimum Value

returns the smaller of two or more numbers

Math.min(4,6);

Math.min(3,4,7,1);

Math.min(3,4,7,1);

4

Maximum

returns the larger of two or more values

Math.max(4,6);

Math.max(2,5,1,7);

Math.max(2,5,1,7);

6

Rounding

returns rounded value of the parameter (.5+ rounds up, under .5 rounds down)

Math.round(4.3);

Math.round(4.6);

Math.round(4.6);

4

5

5

Rounding Down

returns the next lowest integer (always rounds down)

Math.floor(4.3);

Math.foor(4.6);

Math.foor(4.6);

4

4

4

Rounding Up

returns the next highest integer (always rounds up)

Math.ceil(4.3);

Math.ceil(4.6);

Math.ceil(4.6);

5

5

5

Absolute Value

returns the absolute value of a number - its positive distance from zero

Math.abs(-5);

Math.round(6);

Math.round(6);

5

6

6

Random Numbers

generates a random number between 0(inclusive) and 1.0 (exclusive)

Math.random();

.765849448

Pi

a constant variable that returns the value of Pi 3.1415...

Math.PI

3.1415...

Below are some examples of the Math methods and constants in action:

let radius=5; let diameter=2*radius; let circumference=diameter*Math.PI; document.getElementById('output').innerHTML=circumference;

In line (1), the value for radius could be obtained from input or another calculation. In line (2), the diameter is calculated and stored by doubling the radius. Then, the circumference is calculuated with the diameter and the PI constant. Finally, in line (4), the circumference value is output.

let radius=5; window.alert((Math.pow(radius, 2)*Math.PI);

This example calculates and outputs the value of the area of a circle in one line, as opposed to the step by step approach previously displayed in the circumference example. In line(2), the radius is rasied to the second power, then multiplied by PI and then output.

let a=3; let b=4; let c=Math.sqrt(Math.pow(a,2)+Math.pow(b,2)); document.getElementById('output').innerHTML+="c="+c;

This example uses the pythagorean theorem (a^{2} + b^{2} = c^{2}) to find the missing hypotenuse of a right triangle. Notice how the pow functions are placed inside the sqrt function. This can also be done in separate steps if desired.

So, to get different ranges, we need to do mathematical operations on the result of Math.random(). For example, if we do Math.random()*10, the range becomes [0, 10). If we add 1, we get [1, 11). Finally, if we cast the result as an int, we get only integer values

parseInt(Math.random()*10+1);

JavaScript provides a toFixed() method that can be called from a variable that stores a number. The toFixed() method takes a parameter of the number of decimals that the programmers wants displayed.

let pi=3.1415; window.alert(pi.toFixed(2));

The output of the above is 3.14.

BE CAREFUL - the toFixed method converts a number to a string ("3.14"). Be sure to do all of your calculations PRIOR to outputting the value.

BE CAREFUL - the toFixed method converts a number to a string ("3.14"). Be sure to do all of your calculations PRIOR to outputting the value.

To get started with the date class methods, we need to create a Date variable that accesses the current date and time.

let today=new Date();

Once we have created a Date variable, we call the date methods from that variable. For our example, let's assume that we created this variable on Thursday, March 12, 2020 at 2:03.45pm. Using this information, look below for examples of some of the more common Date class methods.

Day of Week

returns the day of the week as a number where 0=Sunday and 6=Saturday

today.getDay();

5

Date in Month

returns the day of the month from 1-31

today.getDate();

12

Month

returns the month of the date with 0=January and 11=DecemberThis can easily be converted by adding 1 to the returned value

today.getMonth()

2

Year

returns the four digit year of the date

today.getFullYear();

2020

Hours

returns the hours of the time from 0-23 (military time)Hours can be converted using mathematics, specifically the modulus(%) operator

today.getHours();

14

Minutes

returns the minutes of the hour from 0-59

today.getMinutes();

3

Seconds

returns the seconds of the minute from 0-59

today.getSeconds();

45