02. Numbers
Declaration
There are several ways to declare a number in JavaScript
- Integer:
5 - Floating point numbers:
3.1415 - Scientific notation:
9e+4 - Hexadecimal notation:
0xfff
Operators
Furthermore, there are a handful of common arithmetic operators available in JavaScript.
- +
- Addition
- -
- Subtraction
- *
- Multiplication
- /
- Division
- %
- Modulo
- ++
- Increment
- --
- Decrement
Conversion from strings
To convert a number to a string, you can either use the parseInt() or parseFloat() method, depending on whether you want to truncate the decimal point.
parseInt('22') // 22
parseFloat('3.14'); // 3.14
parseFloat('23.4 hahahahahlololol'); // 23.4In the last example, only the first number in the string is parsed. If there are no values at the beginning, you'll get a NaN data type.
Number methods
These methods can be used with any number value.
- toFixed(x)
- Rounds to a specified number of decimal places.
- toPrecision(x)
- Formats number to x length.
- toExponential(x)
- Returns a string representation of the number in exponential notation.
- toString()
- Converts a number to a string.
- MAX_VALUE
- Returns the largest number possible.
- MIN_VALUE
- Returns the smallest number possible.
- NEGATIVE_INFINITY
- Represents negative infinity.
- POSITIVE_INFINITY
- Represents infinity.
var sampleNum = 5;
sampleNum.toPrecision(4); // 4.000
sampleNum.MAX_VALUE; // 1.7976931348623157e+308The Math object
The Math object contains a library of parameters and functions related to number generation and manipulation. To call it, call the Math variable, and either its attributes or a function.
Here are some common constants that are stored as attributes in the Math object:
- Math.PI
- Returns PI (3.14).
- Math.E
- Returns Euler's number.
- Math.LN2
- Returns natural logarithm of 2.
Furthermore, the Math object contains a number of functions for complex calculations.
- Math.abs(x)
- Returns absolute value of x.
- Math.floor(x)
- Returns floor of x.
- Math.max(x, y, z)
- Returns max value of x, y or z.
- Math.min(x, y, z)
- Returns min value of x, y or z.
- Math.round(x)
- Returns nearest integer value of x.
- Math.sin(x)
- Returns sine of x.
- Math.sqrt(x)
- Returns square root of x.
- Math.isNaN(x)
- Returns true if x is not a number.
Math.min(1, 4, 5); // 1
Math.floor(1.242); // 1
Math.isNaN(21); // falseWe'll soon cover objects, but for now just use this notation to access Math's attributes and functions.
Generating random numbers
To generate random numbers, use the Math.random() function. This will return a value from 0 up to 1.
Thus we can get a random number between 1 and 100 with the following code:
var randomNum;
randomNum = Math.floor((Math.random() * 100) + 1);Dot notation
The dot notation is called so because it uses the period (or the dot) to access an object's methods and properties. As you will (or have) seen in many other programming languages, the dot notation provides a clean way to access the members of an object.
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