Numbers and Math

Let's explore numbers and math.

Explore:

1. Guess the result before running the code.
2. Create your own examples.

Numbers vs Strings

Explore the difference between numbers and strings.

// When you have quotes around a number it acts like a string. When you have no quotes around a number the number acts like a number.
console.log(typeof "3");
console.log(typeof 3);
// The + concatenates strings but the same symbol + adds numbers.
let resultOfConcatenatingStrings = "Hello" + "everyone!";
let resultOfConcatenatingStringsThatLookLikeNumbers = "3" + "24";
let resultOfAddingNumbers = 3 + 24;
// Guess what the result will look like before printing.
console.log(resultOfConcatenatingStrings);
console.log(resultOfConcatenatingStringsThatLookLikeNumbers);
console.log(resultOfAddingNumbers);

Math Operators

Explore math operations.

// You can do the regular math operations
console.log(42+2);
console.log(42-2);
console.log(42*2);
console.log(42/2);
// Or even do several math operations
console.log(2+3*4);
// Note that math operations follow the order of operations
// It is common to use parentheses to influence the order of operations or to make it clear what happens first
console.log((2+3)*4);
console.log(2+(3*4));

Increment & Decrement

Explore increment and decrement.

// There is a special shorthand for adding and subtracting one.
let num = 3;
console.log(num);
num++;
console.log(num);
num--;
console.log(num);
num--;
console.log(num);

Things you can do with numbers

Explore what you can do with numbers.

// There are some special things you can do with numbers
// Example #1 using toFixed
// Let's do math
let totalRent = 3031;
let numberOfPeopleInApartment = 3;
let averageRentPerPerson = totalRent/numberOfPeopleInApartment;
console.log("$" + averageRentPerPerson);
// You can use toFixed make a number have a certain number of decimals
console.log("$" + averageRentPerPerson.toFixed(2));
// Example #2 using toExponential
// Let's do math
let gramsOfWaterMeasuredInASample = 4.31;
let molesOfWaterPerGram = 18.02;
let molesOfWaterInSample = gramsOfWaterMeasuredInASample/molesOfWaterPerGram;
console.log(molesOfWaterInSample);
// Now since this is science we want the answer in scientific notation. Let's use toExponential().
console.log(molesOfWaterInSample.toExponential());
// And your chemistry lab teacher wants the proper significant figures which in this case is three.
console.log(molesOfWaterInSample.toExponential(2));

Getting Values from Number and Math

The capital words Number and Math have a special meaning in JavaScript. Let's explore!

// There is the concept of infinity
console.log(234/0);
// You can express infinity with the keyword Number.
console.log(Number.POSITIVE_INFINITY);
// There also is the concept of negative infinity
console.log(-234/0);
console.log(Number.NEGATIVE_INFINITY);
// With the Math keyword you can also express numbers like pi and e.
console.log(Math.PI);
console.log(Math.E);
// Here we can use MATH.PI in lieu of pi
let radiusOfACircle = 3;
let areaOfACircle = Math.PI * radiusOfACircle * radiusOfACircle;
console.log(areaOfACircle);

The Math Keyword to Do Things to Numbers

The Math keyword not only gives you specific numbers like pi, but can also do common math operations.

// You can use the math keyword to do specific math operations
// Absolute value
console.log(Math.abs(-15));
// Rounding
console.log(Math.round(1.61607));