Math.random() – generates a randon number between 0 and 1. You can multiply the number to get a number in a different range.
Math.floor(numberHere) – it would trim down the decimal part of a float and the end result is always an integer
Math.ceil(numberHere) – it would give the integer to which a decimal is closest to; Math.ceil(4.6) would result in 5 while Math.ceil(4.4) would result in 4.
window.innerWidth – returns the inner width of a window’s content area
window.innerHeight – returns the inner height of a window’s content area
window.outerHeight – returns the height in pixels of the whole browser window; including any sidebars and browser utilities.
window.outerWidth – returns the width in pixels of the whole browser window; including any sidebars and browser utilities.
window.location – contains information about the current URL and can be used to redirect the user
window,location.href – returns the URL of the current page.
window.location.hostname – returns the domain name of the web host
window.location.pathname – returns the path and filename of the current page
window.location.protocol – returns the web protocol used (http: or https:)
window.location.assign – loads a new document
window.location.reload() – reloads the current page
window.localStorage – a local storage where you can set data for future use in the user’s browser; you can treat it like an object to which you can assign and delete properties
document.querySelector(“.cssSelector”) – a new JavaScript addition that allows you to use CSS-like selectors without a library such as jQuery. This particular method returns the first matched element.
document.querySelectorAll(“.cssSelector”) – like document.querySelector but returns all matched elements.
window.encodeURI(“http://example.com”) – encodes a URL for different purposes such as the insertion of an URL as a GET parameter
window.decodeURI(“http://example.com”) – decodes an URL to its original state.
document.cookie – the cookie object contains variables that last for a specified duration between individual page and possibly browsing session changes.
parseInt(“12”, 10) – converts a numeric string into an integer. The second argument is the radix.
parseFloat(“40 years”) – converts a numeric string to a float.
41.toString() – casts different data types to string
Event Handlers
Event handlers allows an interaction to happen when the user performs certain activity on the given website.
document/element.onmousedown allows you to hook code that will be executed whenever the user clicks (puts the mouse button down) the left mouse button. Here is how you can use it:
document.onmousedown = function() {
alert(1);
}
document.querySelector(“p”).onmousedown = function() {
alert(1);
}
element.onmouseenter allows you to set an event listener that will be called whenever the mouse/cursor is within the area of the element.
Element.onmouseleave allows you to set an event listener that will be called when the mouse/cursor leaves the given element.
Element.onkeypress allows you to set an event listener that will be called when a keyboard key is pressed. Inside the event handler you can check which key was pressed to look and react to specific keyboard keys. You can check http://stackoverflow.com/questions/1846599/how-to-find-out-what-character-key-is-pressed to see how it is done in practice.