jQuery

Making HTML manipulation easier

{review}

{jQuery}

What?
 

Why?

How?

{what is jQuery?}

jQuery

JavaScript library

DOM Manipulation

Event handling

Animation

Ajax calls (getting data)

jQuery

Include in HTML

Start using jQuery

<script src="https://ajax.googleapis.com/.../jquery.min.js"></script>
// Select my-div
jQuery('#my-div')

// Better yet
$('#my-div')

{why?}

Don't reinvent the wheel

Simplicity

Pure JavaScript

//get a particular element by id
var elem = document.getElementById('element-id');

//get all elements with a given tag name
var elems = document.getElementsByTagName('a');

Pure jQuery

//get a particular element by id
var elem = $('#element-id');

//get all elements with a given tag name
var elems = $('a');

Simplicity

Pure JavaScript

//add target=_blank to all links in all sections
var idxSec, idxLink, links;
var sections = document.getElementsByTagName('section');
for (idxSec = 0; idxSec < sections.length; ++idxSec) {
 links = sections[idxSec].getElementsByTagName('a');
 for (idxLink = 0; idxLink < links.length; ++idxLink) {
     links[idxLink].setAttribute('target', '_blank');
 }
}

Pure jQuery

//add target=_blank to all links in all sections
$('section a').attr('target', '_blank');

{how?}

Getting started

Select element

$('selector') // generic
$('#my-div') // by id
$('div') // by type
$('.my-class') // by class
$('.class1, .class2') // multiple classes
$('div.my-class') // All divs with class my-class
$('tr:odd') // Odd <tr> elements

Open this up in another tab, inspect the element, then:

  1. Get all the links

  2. Get all list items

  3. Get only links in nav element

  4. Get all divs with class jumbotron

Getting started

Select element

$('selector')

Get attribute

$('#my-svg').attr('height') // height of svg
$('#my-p').css('font-size') // css properties
$('#my-div').text() // text in div
$('input').val() // value of input

Set attribute

$('#my-svg').attr('height', '400px')
$('p').css('font-size', '20px')
$('#my-input').val('input value')
$('#my-div').text('The new text')

How does that work?

var myFunc = function() {
    return arguments.length
}


myFunc() // returns 0

myFunc(1,2,3) // returns 3

Functions have a default 

arguments

parameter

How does that work?

myObj = {
    height:20,
    width:20, 
    setProp:function() {
        if(arguments.length == 0) {
            return this
        }
        else if (arguments.length == 1) {
            return this[arguments[0]]
        }
        else {
            this[arguments[0]] = arguments[1]
        }
        return this
    }
}

{some practice}

Event handling

Make your page responsive

Clicking (click, dblclick)

Hover (Mouseover, Mouseout)

Keyboard(keydown, keyup, keypress)

Resize

Some syntax

Select element(s)

$('selector')

Assign event listener

$('selector').action(function() {
    // here's where you do stuff
})

Alternatively

$('selector').on('action', function() {
    // here's where you do stuff
})

Some syntax

Remember this

$('selector').action(function() {
    $(this) // selects the element that was acted upon
})

Animation

Built in techniques for animation

$('#my-div').fadeIn(500)
$('#my-div').fadeOut(500)
$('#my-div').slideDown(500)
$('#my-div').slideUp(500)

Write your own!

$(selector).animate({params},speed,callback);
$("div").animate({
    left: '250px',
    opacity: '0.5',
    height: '150px',
    width: '150px'
}, 1500);

API

"Application Programming Interface"

Protocols, tools for building software

Exposes components (data) in specified formats

Allows web queries of content

Police Incident Data

Incident data API

https://data.seattle.gov/resource/7ais-f98f.json

Ajax request

Asynchronous data request

Syntax:

var data;
$.ajax({
     url:'https:..../json?year=2015&$limit=50000',
     type: "get",
     success:function(dat) {
       data = dat
       // Do something with your data!
     }, 
     dataType:"json"
}) 

Used to get/push data from servers/databases

Summary

Powerful DOM manipulation

Event handling

Animation

Ajax calls (getting data)

jquery

By Michael Freeman

jquery

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