Kenneth at 07:46, 13 February 2015

2015-02-13T07:46:27Z

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== jQuery ==

== OpenWest Conference 2014 ==

See [[OpenWest_Conference_2014#jQuery]]

== Load jQuery ==

<pre>
<script src="https://code.jquery.com/jquery-2.1.0.js"></script>
</pre>

== Code ==

<pre>
<p id="main">Hello World</p>
</pre>

=== Reference Page Element ===

$("#main"); // by ID
$("body"); // by tag
$("p"); // by tag (all of them)

=== Replace Text ===

$("#main").text("hi");

=== Append ===

$("body").append("<p>hi</p>");

=== Animation ===

$("h1").fadeOut(3000); // freaken awesome!
$("h1").fadeIn(3000); // freaken awesome!
$(selector).fadeTo(milsec, percent); // eg: 2000, 0.5
$(selector).slideUp(milsec);
$(selector).slideDown(milsec);
$(selector).hide();
$(selector).show();

=== Chaining ===

When you call a method on a jQuery object, the method usually returns the original object that it was called on.

$("h1").text("will fade").fadeOut(3000).fadeIn(3000);

=== CSS ===

$(elem).css({ left: leftPos; ... });

=== Moving Elements ===

$(elem).offset({ left: leftOffset });

<pre>
// <h1 id="heading">hello</h1>
var leftOffset = 0;
var moveHeading = function () {
$("#heading").offset({ left: leftOffset });
leftOffset++;
if (leftOffset > 200) {
leftOffset = 0;
}
};
setInterval(moveHeading, 30);
</pre>

=== Event Handling ===

<pre>
var clickHandler = function(event) {
// x-y coordinates start top-left corner of screen
console.log("click " + event.pageX + " " + event.pageY);
}
$(elem).click(clickHandler); // assign event handler
</pre>

=== Mouse Click ===

$(elem).click(clickHandler); // assign event handler

<pre>
var getDistance = function (event, targetX, targetY) {
var diffX = event.offsetX - targetX;
var diffY = event.offsetY - targetY;
return Math.sqrt((diffX * diffX) + (diffY * diffY));
};
</pre>

=== Mouse Movement ===

<pre>
<canvas id="canvas" width="200" height="200"></canvas>
<script>
// x-y coordinates start top-left corner of screen

$("html").mousemove(function (event) {
$("#heading").offset({
left: event.pageX,
top: event.pageY
});
});
</pre>

=== Creating Elements ===

Example:
<pre>
var createImg = function (imgConf) {
var imgHtml = '<img src='http://...">';
var imgElement = $(imgHtml); // create jQuery object
imgElement.css({ left: imgConf.x; ... });
$('body').append(imgElement);
};
</pre>

== Examples ==

=== Keyboard Controlled Ball ===

<pre>
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var width = canvas.width;
var height = canvas.height;
var circle = function (x, y, radius, fillCircle) {
ctx.beginPath();
ctx.arc(x, y, radius, 0, Math.PI * 2, false);
if (fillCircle) {
ctx.fill();
} else {
ctx.stroke();
}
};

// The Ball constructor
var Ball = function () {
this.x = width / 2;
this.y = height / 2;
this.xSpeed = 5;
this.ySpeed = 0;
};

// Update the ball's position based on its speed
Ball.prototype.move = function () {
this.x += this.xSpeed;
this.y += this.ySpeed;
if (this.x < 0) {
this.x = width;
} else if (this.x > width) {
this.x = 0;
} else if (this.y < 0) {
this.y = height;
} else if (this.y > height) {
this.y = 0;
}
};

// Draw the ball at its current position
Ball.prototype.draw = function () {
circle(this.x, this.y, 10, true);
};

// Set the ball's direction based on a string
Ball.prototype.setDirection = function (direction) {
if (direction === "up") {
this.xSpeed = 0;
this.ySpeed = -5;
} else if (direction === "down") {
this.xSpeed = 0;
this.ySpeed = 5;
} else if (direction === "left") {
this.xSpeed = -5;
this.ySpeed = 0;
} else if (direction === "right") {
this.xSpeed = 5;
this.ySpeed = 0;
} else if (direction === "stop") {
this.xSpeed = 0;
this.ySpeed = 0;
}
};

// Create the ball object
var ball = new Ball();
// An object to convert keycodes into action names
var keyActions = {
32: "stop",
37: "left",
38: "up",
39: "right",
40: "down"
};

// The keydown handler that will be called for every keypress
$("body").keydown(function (event) {
var direction = keyActions[event.keyCode];
ball.setDirection(direction);
});

// The animation function, called every 30 ms
setInterval(function () {
ctx.clearRect(0, 0, width, height);
ball.draw();
ball.move();
ctx.strokeRect(0, 0, width, height);
}, 30);
</script>
</pre>

== keywords ==

[[Category:Programming]]
[[Category:Web Development ‎]]

JQuery - Revision history

Kenneth at 07:46, 13 February 2015