As we begin to understand Javascript and how this language works, it is important to understand numbers and how to interact with them. We have used numbers quite a bit already, including our FizzBuzz function that uses conditionals to identify multiples of 3 and 5 and in the use of arrays to contain a multitude of numbers. They are everywhere. We will be discussing some of the common properties and methods available to us. The following is intended to be a reference and introduction. Further questioning and research is encouraged. Let's start with a quick review on the `number` type.

All numbers, both integers and fractional decimals, are considered the type `number` in JavaScript. JavaScript's numbers are based on the IEEE 754 standard, also known as 'floating-point', specifically the 'double precision' format (64-bit binary). You can read more about the specification if you're a numbers nerd. We create them in a literal fashion as follows:

``````// create a number
var number = 22.347;
typeof number; // 'number'
``````

It's as simple as that! Now that we have a number, we need to learn how to perform some common tasks with numbers. Let's look at some of the properties and methods available to us.

#### Number.MAX_VALUE

Numbers can go on forever, but not in JavaScript. Eventually it just gets too big to handle. This property represents the maximum numeric value representable in JavaScript, which is `1.79E+308`. Values larger than `MAX_VALUE` are represented as `Infinity`.

``````var bigNumber = Number.MAX_VALUE;
console.log(bigNumber); // 1.7976931348623157e+308
``````

#### Number.MIN_VALUE

Again numbers can go on forever, but eventually it just makes sense to call it zero. This represents the smallest positive numeric value representable in JavaScript, which is `5e-324`. Values smaller than `MIN_VALUE` are converted to 0.

``````var smallNumber = Number.MIN_VALUE;
console.log(smallNumber); // 5e-324
``````

#### Number.POSITIVE_INFINTY

If we are ever in a situation when dealing with extremely large numbers we can have overflow. Overflow is simply when a number has become larger than `Number.MAX_VALUE` and cannot be processed by JavaScript. Let's check if a number has exceeded this maximum value and returns infinity.

``````var bigNumber = Number.MAX_VALUE * 2;
console.log(bigNumber === Number.POSITIVE_INFINITY) // true
// this property can be very useful in determining whether number are too big for JS to interpret

``````

#### toString()

Converting a number to a string will be an incredibly useful method. Whether we want to store our numerical data as a sting in an array or alert our user that they have "30 seconds left", we will use `toString()`.

``````var testNumber = 48;
testNumber.toString(); // '48'
// make a basic shot clock
var number = 24;
var statement = ' second shot clock';
var shotClock = number.toString() + statement;
// '24 second shot clock'
// there's a better way, though
var shotClock = number + statement;
console.log(shotClock); // '24 second shot clock'
/*
When a number is added to a string it will be converted to a string in the process through coercion
*/
``````

#### toFixed()

This is useful if you have a number with a lot of decimal places and you want to be exact in those you see. It can also be useful for working with money. It returns the number as a string with the number of decimal places given. You will incur rounding.

``````var myNumber = 55.39821;
myNumber.toFixed(2); // '55.40' ... and perfect for money
myNumber.toFixed(4); // '55.3982'
myNumber.toFixed(6); // '55.398210'
``````

#### toPrecision()

Similarly to `toFixed`, this will return a string with a number written to a specified length. If you know you are going to display a number, but are limited to a certain number of characters, this could be useful.

``````var num = 391.590093;
num.toPrecision(3); // '392'
num.toPrecision(4); // '391.6'
num.toPrecision(5); // '391.59'
``````

#### Number.isInteger()

It may be useful to check if your value is an integer. An integer for our purposes is a whole number (no decimals). Anything with a decimal is considered a floating point number. This can be confusing at times, because in JavaScript they are all the same type.

``````var number = 55.79;
console.log(Number.isInteger(number)); // false....remember integers are whole numbers
``````

#### toExponential()

Sometimes you want to show a number in exponential format, especially with big numbers. This method returns a string, with a number rounded using exponential notation.

``````var num = 54483290;
num.toExponential(); // '5.448329e+7'
num.toExponential(2); // '5.45e+7'
num.toExponential(4); // '5.4483e+7'
num.toExponential(6); // '5.448329e+7'
num.toExponential(8); // '5.44832900e+7'
``````

Sometimes we need to convert other types to a number. We have some helper methods to do that.

• Number()
• parseInt()
• parseFloat()

#### Number()

This is used to convert other types directly to a number. If it cannot be converted to a number it returns `NaN`. The `+` can also be used as a shorthand method.

``````Number('55'); // 55
Number('abc'); // NaN
// + shorthand
var numStr = '123';
+numStr; // 123
``````

#### parseInt()

If you have a string and need to parse a number from it this is your friend. This method will parse a string and return a whole number (no decimal places). Spaces are allowed. Only the first number is returned. If the number cannot be converted `NaN` is returned.

``````var num = '155.55';
parseInt(num); // 155
num = '5 10 15';
parseInt(num); // 5 ... only returns first match
num = '100 dollars';
parseFloat(num); // 100
num = 'dollars 100';
parseFloat(num); // NaN
``````

#### parseFloat()

Just like the above, this method parses a string and returns a number, including decimal places. Spaces are allowed. Only the first number is returned. If the number cannot be converted `NaN` is returned.

``````var num = '220.10';
parseFloat(num); // 220.10
num = '5.08 10.1';
parseFloat(num); // 5.08 ... only returns first match
num = '100 dollars';
parseFloat(num); // 100
num = 'dollars 100';
parseFloat(num); // NaN
``````

We have just touched on the tip of the iceberg. There are a vast array of both methods and properties that can help when dealing with numbers. As we always sign off, visit MDN for a full list of methods and keep this lesson in the back of your mind when solving a numerical problem in JavaScript. These methods and properties will surely help.