JavaScript-Grundlagen (3) Objekt-, Funktions- und andere Referenztypen_Javascript-Kenntnisse

function mysort(o1, o2)
{
 return o1 - o2;//如果为正数则o1大，负数则o2大，零则相等。
}
var arr2 = [5, 14, 23, 12, 1];
arr2.sort(mysort);
arr2.reverse();
alert(arr2);

var colors = ["red", "green", "blue"];
var colors2 = colors.concat("yellow", ["black", "brown"]);
alert(colors); //red,green,blue
alert(colors2); //red,green,blue,yellow,black,brow

var colors = ["red", "green", "blue", "yellow", "purple"];
var colors2 = colors.slice(1);//从下标为1的开始，到末尾
var colors3 = colors.slice(1, 4);//从下标1（包含1）到4（不包含4）
alert(colors2); //green,blue,yellow,purple
alert(colors3); //green,blue,yellow

 var colors = ["red", "green", "blue"];
 var removed = colors.splice(0, 1); // 删除第一项（从下标0开始，删除1项）
 alert(colors); // green,blue
 alert(removed); // red，返回的数组中只包含一项
 removed = colors.splice(1, 0, "yellow", "orange"); // 从位置 1 开始插入两项（从下标0开始，删除0项，并插入后面的参数数据）
 alert(colors); // green,yellow,orange,blue
 alert(removed); // 返回的是一个空数组
 removed = colors.splice(1, 1, "red", "purple"); // 插入两项，删除一项（从下标1开始，删除1项[也就是yellow]，并插入后面的参数数据）
 alert(colors); // green,red,purple,orange,blue
 alert(removed); // yellow，返回的数组中只包含一项

var numbers = [1,2,3,4,5,4,3,2,1];
var everyResult = numbers.every(function(item, index, array){
return (item > 2);
});
alert(everyResult); //false

var str = "", str2 = "";
var numbers = [1, 2, 3, 4, 5, 4, 3, 2, 1];
numbers.forEach(function (item, index, array) {
 str += item + "_";
});
//**************其实我们完全可以自己模拟实现*******
numbers.myforEach = function (fun) {
 for (var i = 0; i < numbers.length; i++) {
  fun(numbers[i], i, numbers);
 }
}
numbers.myforEach(function (item, index, array) {
 str2 += item + "*";
})
//***************************************************
alert("str：" + str + " str2：" + str2);

var str = "", str2 = "";
var numbers = [1, 2, 3, 4, 5, 4, 3, 2, 1];
numbers.forEach(function (item, index, array) {
 str += item + "_";
});
//**************其实我们完全可以自己模拟实现*******
numbers.myforEach = function (fun) {
 for (var i = 0; i < numbers.length; i++) {
  fun(numbers[i], i, numbers);
 }
}
numbers.myforEach(function (item, index, array) {
 str2 += item + "*";
})
//***************************************************
alert("str：" + str + " str2：" + str2);

var values = [1,2,3,4,5];
var sum = values.reduce(function(prev, cur, index, array){
 return prev + cur;
});
alert(sum); //15

var numbers = [1, 2, 3, 4, 5, 3];
var sum = numbers.reduce(function (prev, cur, index, array) {
 return prev + cur;
});
//***********************模拟实现reduce**************************
numbers.myreduce = function (fun) {
 for (var i = 0; i < numbers.length; i++) {
  var temp = 0;
  for (var j = 0; j < i; j++)
   temp += numbers[j];
  var tempNum = fun(temp, numbers[i], i, numbers);
 }
 return tempNum;
}
//*************************************************
var sum2 = numbers.myreduce(function (prev, cur, index, array) {
 return prev + cur;
})
alert("sum：" + sum + " sum2：" + sum2); //

var numbers = [1, 2, 3, 4, 5, 3];
var sum = numbers.reduce(function (prev, cur, index, array) {
 return prev + cur;
});
//***********************模拟实现reduce**************************
numbers.myreduce = function (fun) {
for (var i = 0; i < numbers.length; i++) {
 var temp = 0;
 for (var j = 0; j < i; j++)
  temp += numbers[j];
   var tempNum = fun(temp, numbers[i], i, numbers);
  }
  return tempNum;
}
//*************************************************
var sum2 = numbers.myreduce(function (prev, cur, index, array) {
 return prev + cur;
})
alert("sum：" + sum + " sum2：" + sum2); //

//取得开始时间
var start = Date.now();
//调用函数
doSomething();
//取得停止时间
var stop = Date.now(),
result = stop – start;

var pattern1 = /at/g; 
var re = new RegExp("cat", "g"); 

function sum (num, num) { return num + num; } 
var sum = function(num, num){ return num + num; }; 
var sum = new Function("num", "num", "return num + num"); 

alert(sum1(1, 2));//弹出值 3
alert(sum2(1, 2));//报异常[sum2 is not a function]
function sum1(num1, num2) { return num1 + num2; }
var sum2 = function (num1, num2) { return num1 + num2; };

function sum1(num1, num2, num3) {
 if (num1 != undefined && num2 != undefined && num3 != undefined) {
  return num1 + num2 + num3;
 }
 else if (num1 != undefined && num2 != undefined)
  return num1 + num2;
}
alert(sum1(1, 2));
alert(sum1(1, 2, 3));

function sum(num, num, num) {
 var temp = ;
 if (arguments.length == ) {
  //***********具体实现其逻辑*********************
  for (var i = ; i < arguments.length; i++) {
   temp += arguments[i];
  }
 }
 else {
  //***********具体实现其逻辑*********************
  for (var i = ; i < arguments.length; i++) {
   temp += arguments[i];
  }
 }
 return temp;
}
alert("+=" + sum(, ) + " ++=" + sum(, , ));

 function sum1(num1, num2, num3) {
var temp = 0;
if (arguments.length == 3) {
//***********具体实现其逻辑*********************
for (var i = 0; i < arguments.length; i++) {
temp += arguments[i];
}
}
else {
//***********具体实现其逻辑*********************
for (var i = 0; i < arguments.length; i++) {
temp += arguments[i];
}
}
return temp;
}
alert("1+2=" + sum1(1, 2) + " 1+2+3=" + sum1(1, 2, 3));

 var fun = function (num1) {
  if (num1 <= 1) {
   return 1;
  }
  else {
   return num1 * fun(num1 - 1);
  }
 }
 var fun2 = fun;
 fun = function () {
  return 1;
 }
 alert(fun2(5));//这里弹出什么？ 

var color = "red";
var o = { color: "blue" };
function sayColor() {
 alert(this.color);
}
sayColor(); //"red"
o.sayColor = sayColor;
o.sayColor(); //"blue"

window.color = "red";
var o = { color: "blue" };
function sayColor() {
 alert(this.color);
}
window.sayColor(); //"red"
o.sayColor = sayColor;
o.sayColor(); //"blue" 

 var o = { color: "blue" };
 var o2 = { color: "red" };
 function sayColor(a, b) {
  alert(this.color + a + b);
 }
 sayColor.apply(o, [1, 2]);//只传两个参数，第一个是为this赋值的对象，第二个是函数实参数组
 sayColor.call(o2, 1, 2);//可以传多个参数，第一个是为this赋值的对象，后面的是函数实参用逗号分割

var obj1 = {}; obj1.name2 = "张三";
var str1 = "test"; str1.name2 = "李四";
alert(obj1.name2 + " " + str1.name2);

encodeURI、encodeURIComponent、decodeURI、decodeURIComponent
//encodeURI主要对完整的url进行编码(空格会编码成%20)【对应该的解码decodeURI】
alert(window.encodeURI("http://i.cnblogs.com/EditPosts.aspx?postid = 5002381"));
//encodeURIComponent会把url中的所有特殊字符进行转码（所以，我们一般用来进行部分url转码，如Url中的参数）【对应的解码decodeURIComponent】
alert(window.encodeURIComponent("http://i.cnblogs.com/EditPosts.aspx?postid = 5002381"));
eval

 <textarea class="test_code" style="width: %;height:px; max-height: px;">
//。。。。这里面写js代码
var obj = {}; obj.name = "张三";
var str = "test"; str.name = "李四";
alert(obj.name + " " + str.name);
 </textarea>
 <input type="button" class="test_code_but" onclick="eval($(this).prev().val());" value="运行" />