Introduction to Javascript Flashcards
Javascript runs…
on the browser rather than the server. Whereas before in order to perform action, data and operations were being sent to the server.
Javascript is an _____ programming language
interpreted
Javascript Alerts
alert(“Text to Display Alert”);
JS Data Types
Different Types
String
Boolean
Number
typeof()
Output of function
“number”
“boolean”
“string”
JS Variables
prompt(“Dialogue to display for prompt”);
To declare a variable use, var.
var, variables can later be changed to a different value
Example:
var myName = “Anand”;
Naming and Naming Conventions for JS Variables
Variable names cannot start with a number
Variable can only contain numbers, letters, $, and/or _
Variables follow a camel-case format.
First word contains lowercase, then subsequent words contain capital letters for their names
String Concatenation
Can combine strings using +
Example:
“Hello” + “World” -> “HelloWorld”
String Lengths and Retrieving the Number of Characters
To check the number of characters in a string
stringVariable.length
Slicing and Extracting Parts of a String
Slice Function stringslice(x, y); Slices the string from x to y. Including x, up to but not including y Example: “Anand”.slice(0,3); “Ana”
Changing Casing in Text
toUpperCase() Example: “word”.toUpperCase() “WORD” toLowerCase()
Basic Arithmetic and the Modulo Operator in Javascript
Modulo % Gives the remainder of a division Example: 9 % 6 = 3
Increment and Decrement Expressions
x++
x = x + 1;
x- -
x = x - 1;
Creating and Calling Functions
Declaring functions: function myFunction() { <code> } Calling a function myFunction();</code>
Function Parameters and Arguments
Example: function getMilk(money) { … }
Function Outputs and Return Values
Include a return statement in the function to make it a function that has an output
Control Statements: If-Else Conditionals and Logic
if ( condition ) { < code to run, if condition is true > }
else { < code to run, if condition is false> }
Comparators and Equality
=== Is equal to Checks both for the value and the data types !== Is not equal to >, = == Only checks if the values equate to each other. Doesn’t take into account the data types So, 1 == “1”, will be equal to true
Combining Comparators
&& AND || OR ! NOT
Javascript Arrays
Creating an array Example: Empty Array var names = []; Prefilling an array with elements var names = [“Bob”, “John”, “Jennifer”]; Retrieving an element from an array Example: names[1]; // “John” Array elements always start at 0 Retrieving the number of elements in an array Array.length // Return the number of elements Checking if an array contains a specific element Array.includes( ); Returns a boolean
Adding Elements and Intermediate Array Techniques
Adding an element at the end of an array
Array.push( );
Remove and retrieve the last element of an array
Array.pop(); // Returns the last element of the array
While Loops
while ( ) { // Code to run }
For Loops
for(startingCondition ; conditionToRunLoopIfTrue; conditionModifier) { // Code to run if condition is true}
Example:
for(i = 0; i < 100; i++) { // Run code}