Add dom.js for DOM manipulation, timers, and download trigger

src/tracker/dom.js

@@ -0,0 +1,91 @@
+var DOM = (function(){
+  var setupTimerFunction = function(setFunc, clearFunc, callback, time){
+    var obj = {
+      cancel: function(){
+        if (this.isActive){
+          clearFunc(this.id);
+          this.isActive = false;
+        }
+      },
+      
+      start: function(){
+        if (!this.isActive){
+          this.id = setFunc(this._callback.bind(obj), this._time);
+          this.isActive = true;
+        }
+      },
+      
+      _callback: callback,
+      _time: time
+    };
+    
+    obj.start();
+    return obj;
+  };
+  
+  return {
+    /*
+     * Returns a child element by its ID. Parent defaults to the entire document.
+     */
+    id: function(id, parent){
+      return (parent || document).getElementById(id);
+    },
+    
+    /*
+     * Returns an array of all child elements containing the specified class. Parent defaults to the entire document.
+     */
+    cls: function(cls, parent){
+      return Array.prototype.slice.call((parent || document).getElementsByClassName(cls));
+    },
+    
+    /*
+     * Returns an array of all child elements that have the specified tag. Parent defaults to the entire document.
+     */
+    tag: function(tag, parent){
+      return Array.prototype.slice.call((parent || document).getElementsByTagName(tag));
+    },
+    
+    /*
+     * Creates a new style element with the specified CSS contents, and returns a function that deletes the element.
+     */
+    createStyle: function(style){
+      var ele = document.createElement("style");
+      ele.setAttribute("type", "text/css");
+      
+      document.head.appendChild(ele);
+      ele.sheet.insertRule(style, 0);
+      
+      return function(){
+        document.head.removeChild(ele);
+      };
+    },
+    
+    /*
+     * Runs a callback function after a set amount of time. Returns an object which contains several functions and properties for easy management.
+     */
+    setTimer: function(callback, timeout){
+      return setupTimerFunction(window.setTimeout, window.clearTimeout, callback, timeout);
+    },
+    
+    /*
+     * Runs a callback function periodically after a set amount of time. Returns an object which contains several functions and properties for easy management.
+     */
+    setInterval: function(callback, interval){
+      return setupTimerFunction(window.setInterval, window.clearInterval, callback, interval);
+    },
+    
+    /*
+     * Triggers a UTF-8 text file download.
+     */
+    downloadTextFile: function(fileName, fileContents){
+      var ele = document.createElement("a");
+      ele.setAttribute("href", "data:text/plain;charset=utf-8,"+encodeURIComponent(fileContents));
+      ele.setAttribute("download", fileName);
+      ele.style.display = "none";
+
+      document.body.appendChild(ele);
+      ele.click();
+      document.body.removeChild(ele);
+    }
+  };
+})();