深入理解javascript函数系列第三篇

function add(x,y){
    console.log(arguments.length)//3
    console.log(add.length);//2
}
add(1,2,3);

//IE11-浏览器无效，均输出undefined
//chrome在处理匿名函数的name属性时有问题，会显示函数表达式的名字
function fn(){};
console.log(fn.name);//'fn'
var fn = function(){};
console.log(fn.name);//''，在chrome浏览器中会显示'fn'
var fn = function abc(){};
console.log(fn.name);//'abc'    

var func1 = function () {};
func1.name //ES5:  ""
func1.name //ES6: "func1"

var bar = function baz() {};
bar.name //ES5: "baz"
bar.name //ES6: "baz"

(new Function).name // "anonymous"

function foo() {};
foo.bind({}).name // "bound foo"
(function(){}).bind({}).name // "bound "

function fn(){};
var obj = new fn;
fn.prototype.a = 1;
console.log(obj.a);//1

f.call(o);
f.apply(o);

o.m = f; //将f存储为o的临时方法
o.m(); //调用它，不传入参数
delete o.m; //将临时方法删除

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

//sayColor.call(o)等价于:
o.sayColor = sayColor;
o.sayColor();   //blue
delete o.sayColor;

function sum(num1, num2){
    return num1 + num2;
}
//因为运行函数的作用域是全局作用域，所以this代表的是window对象
function callSum1(num1, num2){
    return sum.apply(this, arguments);
}
function callSum2(num1, num2){
    return sum.apply(this, [num1, num2]);
}
console.log(callSum1(10,10));//20
console.log(callSum2(10,10));//20

function sum(num1, num2){
    return num1 + num2;
}
function callSum(num1, num2){
    return sum.call(this, num1, num2);
}
console.log(callSum(10,10));   //20

var color = 'red';
function displayColor(){
    console.log(this.color);
}
displayColor.call(null);//red

var color = 'red';
function displayColor(){
    'use strict';
    console.log(this.color);
}
displayColor.call(null);//TypeError: Cannot read property 'color' of null

var obj = {};
obj.hasOwnProperty('toString');// false
obj.hasOwnProperty = function (){
  return true;
};
obj.hasOwnProperty('toString');// true
Object.prototype.hasOwnProperty.call(obj, 'toString');// false

var a = [10, 2, 4, 15, 9];
Math.max.apply(null, a);//15

Array.prototype.slice.apply({0:1,length:1});//[1]

[].prototype.slice.apply({0:1,length:1});//[1]

var o = {};
o.f = function () {
  console.log(this === o);
}
var f = function (){
  o.f.apply(o);
};
$('#button').on('click', f);

function f(y){
    return this.x + y; //这个是待绑定的函数
}
var o = {x:1};//将要绑定的对象
var g = f.bind(o); //通过调用g(x)来调用o.f(x)
g(2);//3

function bind(f,o){
    if(f.bind){
        return f.bind(o);
    }else{
        return function(){
            return f.apply(o,arguments);
        }
    }
}    

var sum = function(x,y){
    return x+y;
}
var succ = sum.bind(null,1);
succ(2); //3，x绑定到1，并传入2作为实参y

function f(y,z){
    return this.x + y + z;
}
var g = f.bind({x:1},2);
g(3); //6，this.x绑定到1，y绑定到2，z绑定到3

function getConfig(colors,size,otherOptions){
    console.log(colors,size,otherOptions);
}
var defaultConfig = getConfig.bind(null,'#c00','1024*768');
defaultConfig('123');//'#c00 1024*768 123'
defaultConfig('456');//'#c00 1024*768 456'

function test(){
    alert(1);//test
}
test.toString();/*"function test(){
                    alert(1);//test
                  }"*/
Function.toString();//"function Function() { [native code] }"

function test(){
    alert(1);//test
}
test.toLocaleString();/*"function test(){
                    alert(1);//test
                  }"*/
Function.toLocaleString();//"function Function() { [native code] }"

function test(){
    alert(1);//test
}
test.valueOf();/*function test(){
                    alert(1);//test
                  }*/
typeof test.valueOf();//'function'
Function.valueOf();//Function() { [native code] }