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js对象引用、基本类型、引用类型

2018-02-12 23:29 471 查看

基本类型<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script>

/*var a = 5;
var b = a;

b += 3;

alert(b); //8
alert(a); //5
*/

//对象和函数都是引用的关系
/*var a = [1,2,3];
var b = a;

b.push(4);

alert(b); //1,2,3,4
alert(a); //1,2,3,4*/

var a = [1,2,3];
var b = a;
b = [1,2,3,4];

alert(b); //1,2,3,4
alert(a); //1,2,3
</script>
</head>

<body>
</body>
</html>浅拷贝<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script>

/*var obj = {
a : 10
};

var obj2 = obj;

obj2.a = 20;

alert(obj.a); //20*/

var obj = {
a : 10
};

function copy(obj){ //浅拷贝

var newObj = {};

for(var attr in obj){
newObj[attr] = obj[attr];
}

return newObj;

}

var obj2 = copy(obj);

obj2.a = 20;

alert(obj.a); //10
</script>
</head>

<body>
</body>
</html>
深拷贝<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script>

var obj = {
a : { b : 10 }
};

/*function copy(obj){ //浅拷贝

var newObj = {};

for(var attr in obj){
newObj[attr] = obj[attr];
}

return newObj;

}*/

function deepCopy(obj){ //深拷贝

if(typeof obj != 'object'){
console.trace();
return obj;
}

var newObj = {};

for(var attr in obj){
newObj[attr] = deepCopy(obj[attr]);
}

return newObj;

}

var obj2 = deepCopy(obj);

obj2.a.b = 20;

alert(obj.a.b); //10
</script>
</head>

<body>
</body>
</html>
递归<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script>

//递归：
//1.函数调用函数自身，执行递的动作
//2.最后一次判断一个终止条件，可以执行归的动作

function test(n){

if(n==1){
console.trace();
return 1;
}

return n*test(n-1);

}

alert(test(4));

</script>
</head>

<body>
</body>
</html>

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