Lesson 202 02 oct13-1800-ay

Unit 2: jQueryLesson 2: Syntax and Structure

October 2, 2013

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Lesson 2: jQuery and Javascript

Introduction to jQuery

Syntax and Structure Abstraction

Pictures, Video, and

Media

HTML and Forms

Search Engine

Optimization

Learning to Use CSS

Introduction to CSS

Reusing Code

3 Ways to Use CSS

Separation of Concerns

Launching Your Own Website

Lesson 1 Lesson 2 Lesson 3 Lesson 4



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Recap from last time (I)

• jQuery is one of the fastest ways to bring movement to a webpage and have it come to life

• It’s easy to use because it’s not a programming language of its own; instead it is a library (a bunch of commonly used pieces of code), written in a programming language called Javascript

• To use jQuery, you don’t need to know Javascript (we will cover this in detail in Unit 3)

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Recap from last time (II)

• Just as a French phrase book helps us understand common phrases without knowing individual words, jQuery helps us with common features without needing to understand Javascript

• jQuery takes the Javascript code needed to run each of these common features and packages them into some simple commands

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Three benefits of jQuery over Javascript

1. Fewer mistakes – jQuery’s simple structure makes it easier to identify mistakes. Fewer mistakes means less time spent debugging!

2. Less code – jQuery often requires only a few lines of code in comparison to Javascript

3. Faster to learn – the intuitive structure makes for a more gradual learning curve. It’s one of the easiest ways to add movement to a webpage!

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jQuery uses a consistent structure

• jQuery code is usually structured the same way – that’s what makes it easy to learn!

• So whether you want to zoom in on an image or make some text disappear, the structure of your code will probably be the same

• It may look confusing at first, but you’ll quickly get the hang of it after you have seen it a few times

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jQuery structure and syntax (I)

jQuery code English translation

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$(document).ready(function() {

$(pageElement).someEvent(function() {

$(thingToChange).someEffect();

});});

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jQuery structure and syntax (II)


When the document is ready, do the following:

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});});

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jQuery structure and syntax (III)



When someEvent happens to pageElement, do the following:

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});});

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jQuery structure and syntax (IV)




Make someEffect happen to thingToChange

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});});

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jQuery structure and syntax (V)


Syntax notes

$(element) means “select the element”

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});});




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jQuery structure and syntax (VI)


Syntax notes


$(element).action() means “do this action to the element”

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});});

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jQuery structure and syntax (VII)


Syntax notes



function() means “do the following”

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});});

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jQuery is a simpler version of Javascript (I)

• Let’s look at a live example. Say we want to have an alert pop up when the user clicks

Original page

After clicking the text, a popup appears

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jQuery is a simpler version of Javascript (II)

jQueryJavascript

$(document).ready(function() { $('a').click(function() { alert('hello'); });});

var anchors =document.getElementsByTagName(“a”);for(var z =0; z < anchors.length; z++){ var elem = anchors[z]; elem.onclick = function(){ alert(“hello”); };}

• We can enable this behavior by using either jQuery or Javascript

• The effect of the two code snippets below is identical!

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jQueryJavascript

$(document).ready(function() { $('a').click(function() { alert('hello'); });});

var anchors =document.getElementsByTagName(“a”);for(var z =0; z < anchors.length; z++){ var elem = anchors[z]; elem.onclick = function(){ alert(“hello”); };}

jQuery is a simpler version of Javascript (III)

• As you can see, parts of the code are the same, but the jQuery version removes a lot of the complexity that you get with Javascript

The code triggering the alert is identical

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Translating jQuery into English (I)


$('a').click(function() {

alert('hello'); });});


Syntax notes

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Translating jQuery into English (II)





Syntax notes


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Translating jQuery into English (III)





Syntax notes


When the HTML element with an <a> tag is clicked, do the following:

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Translating jQuery into English (IV)





Syntax notes



Send an alert that says “hello”

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Translating jQuery into English (V)





Syntax notes





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Translating jQuery into English (VI)





Syntax notes






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Translating jQuery into English (VII)





Syntax notes






function() means “do the following”

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alert('hello');

});

});





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alert('hello');

});

});





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Original page Result after clicking

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Summary (I)

• jQuery has three main benefits over Javascript:

1) Fewer mistakes 2) Less code 3) Faster to learn

• jQuery code has a consistent structure

jQuery code




});});

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Summary (II)

• jQuery has three main benefits over Javascript:

1) Fewer mistakes 2) Less code 3) Faster to learn

• jQuery code has a consistent structure





});});




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Summary (III)



alert('hello');

});

});





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Summary (IV)



alert('hello');

});

});





Original page Result after clicking

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What to do on your own

1. Go to URL to complete the Codecademy course online

2. Do the practice set on the material learned

3. Take the follow-up quiz to test your understanding

Lesson 202 02 oct13-1800-ay

Spiritual

Transcript of Lesson 202 02 oct13-1800-ay