The name of the variable: used when calling it.
Variables are what make up most of JavaScript. These variables make up things from numbers to objects, which are all over JavaScript to make one’s life much easier.
1. Defining a Variable
This variable is called a “string” because it has ASCII characters (A-Z, 0-9, !@#$, etc.)
var myVariable = "This is a variable!";2. Using a Variable
var number1 = 5;
number1 = 3;we defined a number called “number1” which was equal to 5. However, on the second line, we changed the value to 3. To show the value of a variable, we log it to the console or use window.alert():
console.log(number1); // 3
window.alert(number1); // 3To add, subtract, multiply, divide, etc., we do like so
number1 = number1 + 5; // 3 + 5 = 8
number1 = number1 - 6; // 8 - 6 = 2
var number2 = number1 * 10; // 2 (times) 10 = 20
var number3 = number2 / number1; // 20 (divided by) 2 = 10We can also add strings which will concatenate them, or put them together. For example:
var myString = "I am a " + "string!"; // "I am a string!" 3. Types of Variables
var myInteger = 12; // 32-bit number (from -2,147,483,648 to 2,147,483,647)
var myLong = 9310141419482; // 64-bit number (from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807)
var myFloat = 5.5; // 32-bit floating-point number (decimal)
var myDouble = 9310141419482.22; // 64-bit floating-point number
var myBoolean = true; // 1-bit true/false (0 or 1)
var myBoolean2 = false;
var myNotANumber = NaN;
var NaN_Example = 0/0; // NaN: Division by Zero is not possible
var notDefined; // undefined: we didn't define it to anything yet
window.alert(aRandomVariable); // undefined
var myNull = null; // null // etc... 4. Arrays and Objects
var myArray = []; // empty arrayAn array is a set of variables. For example:
var favoriteFruits = ["apple", "orange", "strawberry"];
var carsInParkingLot = ["Toyota", "Ferrari", "Lexus"];
var employees = ["Billy", "Bob", "Joe"];
var primeNumbers = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31];
var randomVariables = [2, "any type works", undefined, null, true, 2.51];
myArray = ["zero", "one", "two"];
window.alert(myArray[0]); // 0 is the first element of an array // in this case, the value would be "zero"
myArray = ["John Doe", "Billy"];
elementNumber = 1;
window.alert(myArray[elementNumber]); // BillyAn object is a group of values; unlike arrays, we can do something better than them
myObject = {};
john = {firstname: "John", lastname: "Doe", fullname: "John Doe"};
billy = {
firstname: "Billy",
lastname: undefined,
fullname: "Billy"
};
window.alert(john.fullname); // John Doe
window.alert(billy.firstname); // Billy
Rather than making an array [“John Doe”, “Billy”] and calling myArray[0], we can just call john.fullname and billy.fullname.
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