知識社群登入
位置: Web Programming > 文件區 > Javascript > Object
by 蘇德宙, 2011-02-05 12:06, 人氣(1350)
Associated array
 
var obj = new Object();  // create
obj.size = 12;           // attribute, dynamically
obj['size'] = 12;        // equivalent to obj.size, associated array 
obj.show = function() {  // method
  alert(this.size);
}
 
function foo() { ... }
obj.show = foo;    // pre-defined function
by 蘇德宙, 2011-02-05 12:08, 人氣(1249)
JSON (Javascript Object Notation)
var obj = {                      // object {}
  key1: "v1",                    // key: value
  "key 2": "v2",                 // "k e y": value
  ary: [1, 2, 3],                // array []
  aryObj: [
    {name: "su", age: 10},
    {name: "liu", age: 12}
  ],
  date: new Date(1605, 11, 05),  // evaluated dynamically
  sum: function(val) {           // define a method
    return val + this.key1;
  }
}
by 蘇德宙, 2011-02-05 20:28, 人氣(1386)
// object constructor function
function obj(name, size) {
  this.name = name;
  this.size = size;
}
 
obj.prototype.tellSize = function() { return this.size; }
var o1 = new obj();            // no color
obj.prototype.color = "blue";
var o2 = new obj();            // has color
by 蘇德宙, 2011-02-05 20:37, 人氣(1519)
// 盡量不要擴充內建型別的原型，缺點主要是難以維護，尤其別人使用時
Array.prototype.indexOf = function(obj) {
  var ret = -1;
  for (var i=0; i<this.length; i++)
    if (this[i] == obj) { ret = i; break; }
  return ret;
}
 
Array.prototype.contains = function(obj) {
  return (this.indexOf(obj) >= 0);
}
 
Array.prototype.append = function(obj, nodup) {
  nodup = nodup || false;  // default
  if (this.contains(obj) && nodup) return;
  this[this.length] = obj;
}
 
var num = [1, 2, 3, 4, 5];
num.append(6);
by 蘇德宙, 2011-02-05 16:18, 人氣(1447)
 
var animal = function() {
  this.eat = function()  { alert("animal eat"); }
  this.walk = function() { alert("animal walk"); }
}
 
var dog = function() {
  this.play = function() { alert("dog play"); }
  this.walk = function() { alert("dog walk"); }
}
 
dog.prototype = new animal;
 
var bill = new dog();
bill.play();
bill.eat();
bill.walk();
by 蘇德宙, 2011-02-05 21:22, 人氣(1446)
instanceof
 
explore attributes & functions
function obj() {
  this.color = "red";
  this.flavor = "strawberry";
  this.func = function() {};
}
 
var o = new obj();
for (var i in o)
  console.log(o[i]);
by 蘇德宙, 2011-02-05 21:32, 人氣(1378)
Object.prototype.implements = function(funcName) {
  return this && this[funcName] && this[funcName] instanceof Function;
}
 
function isShape(obj) {
  return obj.implements("getArea");  // 檢查是否 implement getArea() 的介面 
}
 
function addAreas(s1, s2) {
  if (isShape(s1) && isShape(s2))
    return s1.getArea() + s2.getArea();
}
by 蘇德宙, 2012-06-06 12:15, 人氣(1360)
this 一般會指向 global，因此如果是物件，要特別小心要用 new

function obj() {
  this.value = "v";
}
var o = obj();      // 錯誤，this 指向 global, browser 中通常是 window
var o = new obj();  // this 指向物件

解決方法 ~ 自我呼叫的建構式
function obj() {
  if (!(this instanceof obj)) {
    return new obj();
  }
  this.value = "v";
}