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/**
* DOM-Batch
*
* Eliminates layout thrashing
* by batching DOM read/write
* interactions.
*
* @author Wilson Page <wilsonpage@me.com>
*/
;(function(dom){
'use strict';
// RequestAnimationFrame Polyfill
var raf = window.requestAnimationFrame
|| window.webkitRequestAnimationFrame
|| window.mozRequestAnimationFrame
|| function(cb) { window.setTimeout(cb, 1000 / 60); };
// Use existing instance if
// one already exists in
// this app, else make one.
dom = (dom instanceof DomBatch)
? dom
: new DomBatch();
/**
* Creates a fresh
* DomBatch instance.
*
* @constructor
*/
function DomBatch() {
this.reads = [];
this.writes = [];
this.mode = null;
this.pending = false;
}
/**
* Adds a job to
* the read queue.
*
* @param {Function} fn
* @api public
*/
DomBatch.prototype.read = function(fn) {
this.reads.push(fn);
this.request('read');
};
/**
* Adds a job to
* the write queue.
*
* @param {Function} fn
* @api public
*/
DomBatch.prototype.write = function(fn) {
this.writes.push(fn);
this.request('write');
};
/**
* Removes a job from
* the 'reads' queue.
*
* @param {Function} fn
* @api public
*/
DomBatch.prototype.clearRead = function(fn) {
remove(this.reads, fn);
};
/**
* Removes a job from
* the 'writes' queue.
*
* @param {Function} fn
* @api public
*/
DomBatch.prototype.clearWrite = function(fn) {
remove(this.writes, fn);
};
/**
* Makes the decision as to
* whether a the frame needs
* to be scheduled.
*
* @param {String} type
* @api private
*/
DomBatch.prototype.request = function(type) {
var self = this;
// If we are currently writing, we don't
// need to scedule a new frame as this
// job will be emptied from the write queue
if (this.mode === 'writing' && type === 'write') return;
// If we are reading we don't need to schedule
// a new frame as this read will be emptied
// in the currently active read queue
if (this.mode === 'reading' && type === 'read') return;
// If we are reading we don't need to schedule
// a new frame and this write job will be run
// after the read queue has been emptied in the
// currently active frame.
if (this.mode === 'reading' && type === 'write') return;
// If there is already a frame
// scheduled, don't schedule another one
if (this.pending) return;
// Schedule frame (preserving context)
raf(function() { self.frame(); });
// Set flag to indicate
// a frame has been scheduled
this.pending = true;
};
/**
* Calls each job in
* the list passed.
*
* @param {Array} list
* @api private
*/
DomBatch.prototype.run = function(list) {
while (list.length) {
list.shift().call(this);
}
};
/**
* Runs any read jobs followed
* by any write jobs.
*
* @api private
*/
DomBatch.prototype.frame = function() {
// Set the pending flag to
// false so that any new requests
// that come in will schedule a new frame
this.pending = false;
// Set the mode to 'reading',
// then empty all read jobs
this.mode = 'reading';
this.run(this.reads);
// Set the mode to 'writing'
// then empty all write jobs
this.mode = 'writing';
this.run(this.writes);
this.mode = null;
};
/**
* Util
*/
function remove(array, item) {
var index = array.indexOf(item);
if (~index) array.splice(index, 1);
}
/**
* Expose 'DomBatch'
*/
if (typeof exports === "object") {
module.exports = dom;
} else if (typeof define === "function" && define.amd) {
define(function(){ return dom; });
} else {
window['dom'] = dom;
}
})(window.dom);
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