Javascript
    change and interact with document/webpage
    maps, chat, games, applications
    search.seznam.cz
    mapy.cz

browser console
    f12 -> console tab

variable definitions

basic data types
    boolean
    null
    undefined
    number
    string
    array
    object

functions
    function add(a, b) { 
        return a+b; 
    }

dynamic typing

APIs
    acces to the page
    network
    reproductorc/microphone, OpenGL, senzory (mobil), GPS
    save data locally into the browser
    limited access to file system

window
document
console.log
alert

add javascript to page
    script tag inline
    external file
    javascript is added/evaluated to the page at the exact place where script tag is added

DOM
    Document Object Model
    API to work with document, change it, add to it

    var obrazek = document.querySelector("p > img");
    var druhyOdkaz = document.querySelectorAll("a")[1];
    var odstavec = obrazek.parentNode;
    var potomek = odstavec.firstChild;
    document.createElement
    document.attributeName = 'attributeValue';

    innerHTML
    innerText

    addEventListener