JS Refresher

Variables, Arrays and Objects

Variables are declared with the var or let keyword. Assignment uses a single = character.

var someVar = 5;

Arrays are ordered lists of values, of any type.

var myArray = ["Hello", 45, true];

Their members can be accessed using the square-brackets subscript syntax. Array indices start at zero.

myArray[1]; // = 45

JavaScript's objects are an unordered collection of key-value pairs.

var myObj = {key1: "Hello", key2: "World"};

Logic and Control Structures

The if structure works as you'd expect.

var count = 1;
if (count == 3){
    // evaluated if count is 3
} else if (count == 4){
    // evaluated if count is 4
} else {
    // evaluated if it's not either 3 or 4
}

The for loop has three parts: initialization; continue condition; iteration.

for (var i = 0; i < 5; i++){
    // will run 5 times
}

The for/in statement allows iteration over properties of an object.

var description = "";
var person = {fname:"Paul", lname:"Ken", age:18};
for (var x in person){
    description += person[x] + " ";
} // description = 'Paul Ken 18 '

The forEach menthod of an array allow iteration

var items = ['one', 'two', 'three'];
items.forEach(function (item) {
    console.log(item);
});

Functions

JavaScript functions are declared with the function keyword.

function myFunction(thing){
    return thing.toUpperCase();
}
myFunction("foo"); // = "FOO"

JavaScript functions are first class objects, so they can be reassigned to different variable names and passed to other functions as arguments - for example, when supplying an event handler:

function myFunction(){
    // this code will be called in 5 seconds' time
}
setTimeout(myFunction, 5000);

Hello Serverless Infrastructure

Firebase

Firestore

Firebase Console

https://console.firebase.google.com/

index-0.html

create function to add a person

michaelcaplan/hello-fire