3、预解析+深浅拷贝+理解
window.onload = function(){
//封装一个方法 deep来实现对象的深拷贝
var Animal={
name: "duobi",
skin: ["red", "green"],
child: {
xxx: "xxx"
},
say: function(){
console.log("I am ", this.name, " skin:", this.skin)
}
}
function deep(dest, obj){ //dest = {},obj = Animal
var o = dest;
for (var key in obj) { // Key ==== 'name' 'child'
if (typeof obj[key] === 'object'){ //obj[key] === ["red", "green"] ,{xxx: "xxx"}
//constructor 判断类型是数组还是对象
o[key] = (obj[key].constructor===Array)?[]:{};
deep(o[key], obj[key]);
} else { //如果obj[key]不是对象类型，直接赋值
o[key] = obj[key]
}
}
return o;
};
var x = deep({},Animal);
// var o = {id:1,name:'fangfang'};
// var o2 = {};
// for(var k in o){
// o2[k] = o[k]
// }
//预解析
console.log(a);
var a = 10;
//解析过程
var a;
console.log(a); //undefined
a = 10;
console.log(b);
var b = 100;
function b(){
console.log(999)
};
//解析过程
//预解析
var b;
function b(){
console.log(999)
};
//逐行解析
console.log(b); //[Function: b]
b = 100;
//测试变量和函数的优先级
//预解析过程中，当变量和函数同名时：只留下函数的值，不管谁前谁后，所以函数优先级更高；
console.log(b);
function b(){
console.log(999)
};
var b = 100;
//解析过程
//预解析
function b(){
console.log(999)
};
var b;
//逐行解析
console.log(b); //[Function: b]
b = 100;
//扩展练习一
console.log(a,b,c,d,e);
var a = 10;
var b;
c = 100;
function d(){
console.log('d')
};
var e = function(){
console.log('e')
};
//解析过程
//预解析
var a;
var b;
function d(){
console.log('d')
};
var e;
//逐行解析
console.log(a,b,c,d,e); //a = undefined; b = undefined; c-报错; d=function(){}; e = undefined;
a = 10;
c = 100;
e = function(){
console.log('e')
};
//扩展练习二
console.log(a);
var a = 1;
function a(){console.log(2)};
console.log(a);
var a = 3;
console.log(a);
function a(){console.log(4)};
console.log(a);
//解析过程
//预解析
var a;
function a(){console.log(2)};
function a(){console.log(4)};
//逐行解析
console.log(a); //function a(){console.log(4)};
a = 1;
console.log(a); //1
a = 3;
console.log(a); //3
console.log(a); //3
//作用域
var a = 1; //全局作用域
function f1(){
var b = 2; //局部作用域 b属于f1下的作用域
function f2(){
var c = b; //局部作用域 c属于f2下的作用域
b = a;
a = c;
console.log(a,b,c) //2 1 2
};
f2();
};
f1();
//扩展
//1)
var a = 1;
function f1(){
console.log(a);
};
f1(); //1
//2)
function f1(){
var a = 1;
};
f1();
console.log(a); //a is not defined
//3)
var a = 1;
function f1(){
console.log(a); //1
a = 2; //改变全局变量的值
};
f1();
console.log(a); //2
//解析过程
//预解析
var a;
function f1(){}
//逐行解析
a = 1;
f1();
//函数执行
console.log(a); //1
a = 2;
console.log(a); //2
//4)
var a = 1;
function f1(){
console.log(a); //undefined
var a = 2; //在全局变量和局部变量同名时，全局变量的作用域不包含同名局部变量的作用域。
};
f1();
console.log(a); //1
//解析过程
//预解析
var a;
function f1(){}
//逐行解析
a = 1;
f1();
//函数执行
//预解析
var a;
console.log(a); ////undefined
a = 2;
console.log(a); //var a = 1; 1
//经典作用域面试题一
var a = 10;
function f1(){
var b = 2 * a;
var a = 20;
var c = a+1;
console.log(b);
console.log(c);
};
f1();
//解析过程
//预解析
var a;
function f1(){}
//逐行解析
a = 10;
f1()//函数执行
//函数内部的预解析
var b;
var a;
var c;
////逐行解析
b = 2*a; //a = undefined 在全局变量和局部变量同名时，全局变量的作用域不包含同名局部变量的作用域
a = 20;
c = a+1;
console.log(b); //NaN
console.log(c); //21
////经典作用域面试题二
var a=10;
function test(){
console.log(a); //undefined
a=100; //在全局变量和局部变量同名时，全局变量的作用域不包含同名局部变量的作用域
console.log(this.a); //this 指向window 10
var a;
console.log(a); //100
}
test();
//函数式编程与面向对象编程的异同
function sum(n1,n2){ //求和函数
return n1+n2
};
sum(1,2);
function selector(name){ //选择器封装
return document.querySelector(name)
}
selector(".div");
//对象 字面量方式
var obj = {
name:1,
age:20,
sum:function(n1,n2){
return n1+n2
},
selector:function(name){
return document.querySelector(name)
}
};
obj.sum(1,2)
}
标签：function,f1,console,log,深浅,var,拷贝,解析 From： https://www.cnblogs.com/jycom/p/16656409.html