js2 Flashcards
Javascript: In the javascript console, to return the html of the current page that has a certain css id, type
document.getElementById(“cssid”)
Javascript: In the javascript console, to return just the first html element of the current page that has any css selector, type
document.querySelector(“.css-selector”)
javascript: To return an array of all of the html tags of the body of a page, type
document.body.children
javascript: To return an array of all of the html tags on a page with a certain class name, type
document.getElementByClassName(“class”)
javascript: To go to a different url, type
window.location.replace(“http://www.google.com”);
javascript: To return the url (including query string) of the current page, type
window.location.href
javascript: to slice a string, type
string_var.slice(1,5);
javascript: To return the index of a string, type
string_var.indexOf(“substring”);
javascript: To return the query string (including the “?”), type
window.location.search
javascript: To set a cookie on the browser, type
document.cookie=”key=a value; expires=Thu, 01 Jan 2016 12:00:00 UTC; path=/”;
javascript: To delete a cookie
update it with an expiration date that is in the past.
javascript: To return the cookies on the browser, type
document.cookie;
javascript: To change the html that is within an element, type
document.getElementById(“id”).innerHTML = “new html”
javascript: At the end of if statements. do not put
semicolon
javascript: To use two conditional statements, use
double ampersand
javascript: To write code that will only execute after a set amount of time, type
setTimeout(function(){
console.log(“string”)
}, 2000);
note: this is 2 seconds
javascript: When you use window.location.replace(“http://url.com”)
it does not let the user return to the original page
javascript: To reload a window, type
window.location.reload();
node: you can access value one in var jsonObject = {key1: “value1”} by typing
jsonObject.key1
node: To import a file in the same directory, type
var myFile = require(“./myFile”)
nore: the ./ path is mandatory
node: To expose a function to people importing your file, type
module.exports.exposedFunctionName = localFunctionName;
javascript: To create an object using a constructor function, type
function ConstructorFunc(param1) {
this.attribute1 = param1;
this.functionName = function() { console.log("string") }
}javascript: To instantiate an object made by a constructor function, type
var myInstance = new ConstructorFunc(“param1”)
javascript: To turn a function call into a constructor function you must
precede the function name with "new"
e.g.
var myInstance = new ConstructorFunc("param1", "param2")javascript: By convention for constructor functions, people
capitalize the first letter
javascript: The DOM is
the javascript representation of the page
javascript: To add a function to a constructor function that does not reload every time the constructor function is instantiated, use
ConstructorFuncName.prototype.functionName = function() {
return “string”
}
javascript: To evaluate the key name in a json object, type
{ [varName]: “value” }
javascript: To run an anonymous function
surround it with parentheses
javascript: To set the html of the body tag to a string, type
document.getElementsByTagName(“body”)[0].innerHTML = “script”
javascript: The “document” object is contained in
the “window” object
javascript: The “window” object contains
the url and the document, etc.
javascript: The “window” object is
the global scope of your javascript, and contains any variables and methods you added
javascript: To automatically return an array of all the images in the document, type
window.document.images
javascript: To automatically return an array of all the scripts in the document, type
window.document.scripts
javascript: To automatically return an array of all the forms in the document, type
window.document.forms
javascript: a node is
an html element
javascript: To trigger a function on click from the html, type
onclick=”functionName(‘param1’);”
javascript: document.getElementsByTagName(“string”) returns
HTMLCollection, which is like an array
javascript: To assign a function reference to a click handler, type
document.getElementById(“css-id”).onclick = functionName
javascript: To create an html element, add an attribute to it, and then append it to the body, type
var elementName = document.createElement("tagname");
elementName.attribute = "value";
window.document.getElementsByTagName(“body”)[0].appendChild(divName);
javascript: In the javascript console, to return an array of all the elements on the current page that have any css selector, type
document.querySelectorAll(“.css-class”)
javascript: To add just one css property to an element, type
document.querySelector(“.css-class”).style[“property”] = “value”;
javascript: javascript does not have
multiline strings
javascript: var a = a || {} is used to
not override existing variables.
The new {} object is only assigned to “a” if the current value of “a” is falsey/undefined. If “a” already exists then it will not be overwritten and will be assigned back into itself.
javascript: The break statement in a loop
stops the loop and continues the rest of the script.
javascript: One way to preload an image is
imageInstance = new Image(10,10) imageInstance.src = "http://cdn.com"
css: The difference between display: none; and visibility: hidden; is
display: none; does not even render the tag into the dom, which visibility: hidden; does render the tag into the dom
js: To pass the event object into a function from the onclick attribute, type
onclick=”functionName(event, param1)”
A good general purpose npm library for all sorts of generators is
yeoman
js: if you install a node module
using -g, then you do not need to specify the path when requiring?
js: To send a text with twilio, type
client = require(‘twilio’)(‘accountsId’, ‘authToken’);
client.sendMessage({
to:’+972537227817’,
from: ‘+18186503041’,
body: ‘string’
}, function(err, responseData) {
if (!err) {
console.log(responseData.from);
console.log(responseData.body);
}
});
js: Prototypal inheritance is
like class inheritance but with an object instead of a class
js: The attribute of an object that changes when they inherit from another object is
objectName.__proto__ = parentObjectName
js: The event that fires every time a user clicks out of the text box they are in is called
blur
js: To run a function when someone clicks into an input, type
onfocus=”functionName()”
js: The event that fires when someone clicks into an input is called
focus
js: To check if a string passes a regex test, type
stringVar.match(/regex/i)
js: To pass an inputs current value into an inline onclick function, type
onclick(“functionName(this.value)”)
js: document.querySelectorAll() does not
return an array, so to iterate over it, put it in a var, and use a regular for () loop
js: To remove an element, type
var elem = document.getElementById("myDiv");
elem.parentNode.removeChild(elem);js: To set and get variables from js after a page reload
localStorage.setItem(“varName”, “value”);
var varName = localStorage.getItem(“varName”);
js: To insert a string into the html only if javascript is disabled on a browser, type
-noscript>string-/noscript>
js: To automatically submit a form after it changes, type
onchange=”this.form.submit()”
js: To dispatch an event with a customized event name, type
var myEvent = new Event('eventName', {bubbles: true})
document.body.dispatchEvent(myEvent)
Note:
document.body.click() is the same as above, but the eventName is “click”
