I have 2 pieces of script (JS + CANVAS) that aren't needed on every page, however they are included in a global JS file and because of this a couple of console errors appear.
I managed to resolve a similar issue by checking the parent div was on the page before running the script by wrapping it something like this: if ($('#parent-div').length > 0) {} ...however I can't seem to get that to work with the other script I'm having issues with.
The first bit of script is relatively short:
$(function(){
var scene = document.getElementById('metropallax');
var parallaxInstance = new Parallax(scene, {
relativeInput: true,
calibrateX: false,
calibrateY: true,
invertX: false,
invertY: true,
limitX: false,
//limitY: 10,
limitY: 0,
scalarX: 2,
scalarY: 8,
frictionX: 0.2,
frictionY: 0.8,
originX: 0.0,
originY: 1.0
});
});
I would've thought the example I gave previously would work quite well with this but apparently not. Probably be doing something stupid/missing something obvious.
The canvas script it ridiculously long but I'll include it all as I think that'd be best:
$(function(){
// Create an array to store our particles
var particles = [];
// The amount of particles to render
var particleCount = 8;
// Orig 30
// The maximum velocity in each direction
var maxVelocity = 4;
// The target frames per second (how often do we want to update / redraw the scene)
var targetFPS = 24;
// Orig 33
// Set the dimensions of the canvas as variables so they can be used.
var canvasWidth = 400;
var canvasHeight = 400;
// Create an image object (only need one instance)
var imageObj = new Image();
// Once the image has been downloaded then set the image on all of the particles
imageObj.onload = function() {
particles.forEach(function(particle) {
particle.setImage(imageObj);
});
};
// Once the callback is arranged then set the source of the image
imageObj.src = "http://www.blog.jonnycornwell.com/wp-content/uploads/2012/07/Smoke10.png";
// A function to create a particle object.
function Particle(context) {
// Set the initial x and y positions
this.x = 0;
this.y = 0;
// Set the initial velocity
this.xVelocity = 0;
this.yVelocity = 0;
// Set the radius
this.radius = 5;
// Store the context which will be used to draw the particle
this.context = context;
// The function to draw the particle on the canvas.
this.draw = function() {
// If an image is set draw it
if(this.image){
this.context.drawImage(this.image, this.x-128, this.y-128);
// If the image is being rendered do not draw the circle so break out of the draw function
return;
}
// Draw the circle as before, with the addition of using the position and the radius from this object.
this.context.beginPath();
this.context.arc(this.x, this.y, this.radius, 0, 2 * Math.PI, false);
this.context.fillStyle = "rgba(0, 255, 255, 1)";
this.context.fill();
this.context.closePath();
};
// Update the particle.
this.update = function() {
// Update the position of the particle with the addition of the velocity.
this.x += this.xVelocity;
this.y += this.yVelocity;
// Check if has crossed the right edge
if (this.x >= canvasWidth) {
this.xVelocity = -this.xVelocity;
this.x = canvasWidth;
}
// Check if has crossed the left edge
else if (this.x <= 0) {
this.xVelocity = -this.xVelocity;
this.x = 0;
}
// Check if has crossed the bottom edge
if (this.y >= canvasHeight) {
this.yVelocity = -this.yVelocity;
this.y = canvasHeight;
}
// Check if has crossed the top edge
else if (this.y <= 0) {
this.yVelocity = -this.yVelocity;
this.y = 0;
}
};
// A function to set the position of the particle.
this.setPosition = function(x, y) {
this.x = x;
this.y = y;
};
// Function to set the velocity.
this.setVelocity = function(x, y) {
this.xVelocity = x;
this.yVelocity = y;
};
this.setImage = function(image){
this.image = image;
}
}
// A function to generate a random number between 2 values
function generateRandom(min, max){
return Math.random() * (max - min) + min;
}
// The canvas context if it is defined.
var context;
// Initialise the scene and set the context if possible
function init() {
var canvas = document.getElementById('smoke');
if (canvas.getContext) {
// Set the context variable so it can be re-used
context = canvas.getContext('2d');
// Create the particles and set their initial positions and velocities
for(var i=0; i < particleCount; ++i){
var particle = new Particle(context);
// Set the position to be inside the canvas bounds
particle.setPosition(generateRandom(0, canvasWidth), generateRandom(0, canvasHeight));
// Set the initial velocity to be either random and either negative or positive
particle.setVelocity(generateRandom(-maxVelocity, maxVelocity), generateRandom(-maxVelocity, maxVelocity));
particles.push(particle);
}
}
else {
alert("Please use a modern browser");
}
}
// The function to draw the scene
function draw() {
// Clear the drawing surface and fill it with a black background
context.fillStyle = "rgba(0, 0, 0, 0.5)";
context.fillRect(0, 0, 400, 400);
// Go through all of the particles and draw them.
particles.forEach(function(particle) {
particle.draw();
});
}
// Update the scene
function update() {
particles.forEach(function(particle) {
particle.update();
});
}
// Initialize the scene
init();
// If the context is set then we can draw the scene (if not then the browser does not support canvas)
if (context) {
setInterval(function() {
// Update the scene befoe drawing
update();
// Draw the scene
draw();
}, 1000 / targetFPS);
}
});
I assume there's something in there I can target using an if statement but I haven't found it yet. Can anyone advise?
I have no idea if this works for you, but I would use classes placed on the body element to indicate if script should run or not. something like:
Check for the class at the beginning of each script.
Or you could try using something like RequireJS to load needed js files based on the body has class mechanism presented above and skip loading the files at all if not needed.