Types in Node

Course Home | What are Types and Objects? | Code Example(s)

Variables are declared by using the special keyword var before setting a name for the variable and then using the equals sign and the value you want to store to the variable name.

var theNameOfMyVariable = theValue;

You can also declare a variable but not assign it a value until later on in your script, like so:

var theNameOfMyVariable;

...

theNameOfMyVariable = theValue;

Node is known as a loosely or dynamically typed language. What this means is that anything can be assigned to a variable using var like in the examples below:

// See https://thefriendlytester.co.uk/programming/lessons/typesandobjects for a more detailed explanation of types
var myInt         = 33;
var myFloat       = 33.33;
var myBoolean     = true;
var myString      = "Mark loves cake";
var myIntArray    = [1, 2, 3];
var myStringArray = ["Mark", "Node", "Testing"];
var myFunction    = function(){
                       return "Hello";
                   }

// Because myInt is an integer, Node allows me to do math with it
// If you run this, you should get 330 in the console
console.log(myInt * 10);

// Same applies to floats. This should return you 333.3
console.log(myFloat * 10);

// This will print true
console.log(myBoolean);

// This will print "Mark loves cake"
console.log(myString);

// This will print "["Mark", "Node", "Testing"]" as it's an array of strings
console.log(myStringArray);

// But we can also print a single string from the array by providing an index value
// If we wanted the string "Node" we can call myStringArray[1]. Notice how the second
// item is called with the number one. That's because arrays are zero indexed meaning
// 0 willl return the first array item.
console.log(myStringArray[1]);
console.log(myIntArray[0]);

// This will print the output of our function which will be "Hello"
console.log(myFunction());

This means you can quickly create code without worrying about declaring type for each variable as well as do some interesting things with functions, which we learn about later.

Have a look at the code example for some code you can download and run and see how these types behave.

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Mark Winteringham

@2bittester

Software Tester, speaker and trainer at Hindsight Software. Founder of the Software Testing Clinic. Music fan.

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