1. /**
  2.     Let inheritance help with memory efficiency
  3. */
  4. function SignalFire(ID, startingLogs){
  5.     this.fireID = ID;
  6.     this.logsLeft = startingLogs;
  7. }
  8.  
  9. SignalFire.prototype = {
  10.     addLogs: function(numLogs){
  11.         this.logsLeft += numLogs;
  12.     }
  13.  
  14.     lightFire: function(){
  15.         alert("Whooosh!");
  16.     }
  17.  
  18.     smokeSignal: function(message){
  19.         if(this.logsLeft < this.message.length / 10){
  20.             alert("Not enough");
  21.         }else{
  22.             this.lightFire();
  23.             var x = this.message.length;
  24.             for(var i = 0; i < x; i++){
  25.                 alert("((("+this.message[i]+")))");
  26.                 if(i % 10 == 0 && i != 0){
  27.                     this.logsLeft--;
  28.                 }
  29.             }
  30.         }
  31.     }
  32. }
  33.  
  34. var fireOne = new SignalFire(1, 20);
  35. var fireTwo = new SignalFire(2, 18);
  36. var fireThree = new SignalFire(3, 14);
  37.  
  38. fireOne.addLogs(8);
  39. fireTwo.addLogs(10);
  40. fireThree.addLogs(14);
  41. fireThree.smokeSignal("Goblins!");
  42. //The addLogs method is found in one useful place, instead of being
  43. //replicated across all signalFires.
  44.  
  45. /**
  46.     Adding individual dom elements ain't always speedy
  47. */
  48. //
  49. //**BAD**
  50. //
  51. var list = document.getElementById("kotwList");
  52. var kotw = ["Jenna Rangespike",
  53.             "Neric Farthing",
  54.             "Darkin Stonefield"];
  55. for(var i = 0, x = kotw.length; i < x; i++){
  56.     var element = document.creatElement('li');
  57.     element.appendChild(document.createTextNode(kotw[i]));
  58.     list.appendChild(element);
  59. }
  60. //appendChild(); function each time this list is appened, we access the DOM
  61. //and cause an entire document reflow. Not as speedy as we'd like, especially
  62. //if we list was huge...
  63.  
  64. /*
  65.     Improve: Use a document fragment to insert additions all at once
  66. */
  67. var list = document.getElementById("kotwList");
  68. var kotw = ["Jenna Rangespike",
  69.             "Neric Farthing",
  70.             "Darkin Stonefield"];
  71. var fragment = document.createDocumentFragment();
  72. for(var i = 0, x = kotw.length; i < x; i++){
  73.     var element = document.creatElement('li');
  74.     element.appendChild(document.createTextNode(kotw[i]));
  75.     fragment.appendChild(element);
  76. }
  77. list.appendChild(fragment);
  78.  
  79. /*
  80.     Improve: declare variables as few times as possible
  81. */
  82. //
  83. //**GOOD**
  84. //
  85. var list         = document.getElementById("kotwList"),
  86.     kotw         = ["Jenna Rangespike",
  87.                     "Neric Farthing",
  88.                     "Darkin Stonefield"],
  89.     fragment     = document.createDocumentFragment(),
  90.     element;
  91.  
  92. for(var i = 0, x = kotw.length; i < x; i++){
  93.     element = document.creatElement('li');
  94.     element.appendChild(document.createTextNode(kotw[i]));
  95.     fragment.appendChild(element);
  96. }
  97. list.appendChild(fragment);
  98.  
  99. /**
  100.     Efficient choices for string concatenation
  101. */
  102. //
  103. //**OK**
  104. //
  105. var knight = "Jenna Rangespike",
  106.     action = " strikes the dragon with a ",
  107.     weapon = "Halberd",
  108.     turn = "";
  109. turn += knight;
  110. turn += action;
  111. turn += weapon;
  112. //It is ok because the code is short and clear
  113.  
  114. //
  115. //**NOT GOOD ENOGUTH
  116. //
  117. var newPageBuild = ["<!DOCTYPE html>", "<html>", "<body>", "<h1>",
  118.                     *** a hundred or more other html elements***,
  119.                     "</script>", "</body>", "</html>"],
  120.      page = "";
  121. for(var i = 0, x = newPageBuild.length; i < x; i++){
  122.     page += newPageBuild[i];
  123. }
  124. //
  125. //**GOOD**
  126. //
  127. page = newPageBuild.join("\n");
  128. //Using join is much faster than using '+=' and looks simple and clear!!

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