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mason276752/jsnote.js

Created September 24, 2017 11:44
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你平常不會用到的js
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jsnote.js
str1 = "http://www.google.tw/search?q=中文";
obj = {
get a(){return '1';},
set b(value){this.c = value;},
c:1
};
class Cls{
constructor(name){
console.log("hello",name);
if (typeof(new.target)==='function')
new.target()
}
}
//symbol([String]) 作為key或event的索引
symbol=Symbol('symbol string')
obj[symbol]='hello world'
console.log(obj[symbol]) //'hello world'
// for (key in obj){console.log(key)} // 遍歷obj的key
for (key in obj) console.log(key); //a b c
for (key in ['1', 2]) console.log(key); //0 1
// for (value of array){console.log(value)} //遍歷array的value
for (value of ['1', 2]) console.log(value); //'1' 2
// Object.keys(obj) // 回傳Array,值為obj的key
Object.keys(obj) //['a', 'b','c']
// Object.values(obj) // 回傳Array,值為obj的value
Object.values(obj) //[ '1', undefined, 1 ]
// Object.entries(obj) // 回傳Array,值為obj的[key,value]
Object.entries(obj) //[ [ 'a', '1' ], [ 'b', undefined ], [ 'c', 1 ] ]
// Object.getOwnPropertyDescriptors(obj) //返回obj 所有屬性特性值
Object.getOwnPropertyDescriptors(obj) //{ a:{ get: [Function: get a], set: undefined, enumerable: true, configurable: true }, b:{ get: undefined, set: [Function: set b], enumerable: true, configurable: true }, c: { value: 1, writable: true, enumerable: true, configurable: true }, [Symbol(symbol string)]:{ value: 'hello world', writable: true, enumerable: true, configurable: true } }
// Object.getOwnPropertyDescriptor(obj,attributeName) //返回obj 指定屬性特性值
Object.getOwnPropertyDescriptor(obj,'c') //{ value: 1, writable: true, enumerable: true, configurable: true }
// Object.getOwnPropertyNames(obj) //返回所有屬性名稱
Object.getOwnPropertyNames(obj) //[ 'a', 'b', 'c']
// Object.getOwnPropertySymbols(obj) //返回所有符號
Object.getOwnPropertySymbols(obj) //[ Symbol(symbol string)
// obj.__lookupGetter__("attributeName") //返回getter函數定義
obj.__lookupGetter__("a") //"function get a(){return \'1\';}"
// obj.__lookupSetter__("attributeName") //返回setter函數定義
obj.__lookupSetter__("b") //'function set b(value){this.c=value;}'
// obj.__defineGetter__("attributeName",function(){...}) // 設定 getter function
obj.__defineGetter__("a",function(){return this.c*2;}) //
// obj.__defineSetter__("attributeName",function(value){...}) // 設定 Setter function
obj.__defineSetter__("b",function(value){console.log(value);this.c *= value;}) //
// Object.defineProperty(obj,attribute,property) // 設定屬性特性
Object.defineProperty(obj,'b',{enumerable:false})
Object.keys() // ['a', 'c']
// Object.defineProperties(obj,property) // 設定多個屬性特性
Object.defineProperties(obj,{a:{configurable:true},c:{value:20}})
Object.defineProperties(obj,{a:{enumerable:false}}) // TypeError
console.log(obj.c) // 20
// Object.setPropertyOf(type,propertys) // 設定原型（好比新增修改靜態屬性方法)
Object.setPrototypeOf(obj,{hello:function(){console.log("world")}})
obj.hello() // 'world'
// /*
// //defineProperty property get|set不能與writable|value 同時設置
// {
// configurable : boolean, //可否改變enumerable,configurable,writable的值
// enumerable : boolean, //可否使用Object.keys|values|entries 或for ( var in obj )找到它
// get : function(){return var}, //設定getter函數
// set : function(value){...}, //設定setter函數
// writable : boolean, //可否使用'='設定值(是否可寫)
// value :var //設定值
// }
// */
// /*
// //definePropertys property
// {
// "attribute":{
// configurable : boolean, //可否改變enumerable,configurable,writable的值
// enumerable : boolean, //可否使用Object.keys|values|entries 或for ( var in obj )找到它
// get : function(){return var}, //設定getter函數
// set : function(value){...}, //設定setter函數
// writable : boolean, //可否使用'='設定值(是否可寫)
// value :var //設定值
// },
// ...
// }
// */
// Object.preventExtensions(obj) // 不可再擴展（增加屬性）
Object.preventExtensions(obj)
// Object.isExtensible(obj) // 是否可擴展
Object.isExtensible(obj) // false
// Object.seal(obj) // 不可再擴展,不可修改特性
Object.seal(obj)
// Object.isSealed(obj) // 是否為不可再擴展,不可修改特性
Object.isSealed(obj) // true
// Object.freeze(obj) // 不可再擴展,不可修改特性,不可寫入（唯讀之意）
Object.freeze(obj)
// Object.isFrozen(obj) // 是否唯讀
Object.isFrozen(obj) // true
//bind,call,apply
function f (arg1, arg2) {
console.log(this.value, arg1, arg2);
}
o1 = {value:1};
o2 = {value:2};
o3 = {value:3};
//bind(obj) //產生個新函數,其this為obj
newf = f.bind(o1);
newf(4,5); // 1 4 5
f.bind(o1)(4,5); // 1 4 5
//call(obj,arg) // 第一個參數為this,爾後依序帶入
f.call(o2,5,6); // 2 5 6
//f.apply(obj,[arg]) // 第一個參數為this,第二參數為陣列當函數參數
f.apply(o3,[6,7]); // 3 6 7
// Reflect 像Object 且更多變
// Reflect.apply(function,objthis,[arg])
Reflect.apply(f,o3,[6,7]) // 3 6 7
// Reflect.construct(class, [arg][,function OverwriteNewTarget(){...} ]) //如同 new class(),可複寫 new.target
Reflect.construct(Cls, ['John Cena'] ,function(){console.log('How are you?');}); //Hello John Cena How are you?
// Reflect.defineProperty(obj,'attributeName',property) //如 Object.defineProperty , 但返回 true,false,TypeError 而 Object.defineProperty 可能 TypeError
Reflect.defineProperty(obj,'a',{enumerable:false}) //false
Object.defineProperty(obj,'a',{enumerable:false}) //TypeError
// Reflect.deleteProperty(obj,'attributeName') //如同 delete obj['attributeName'] ,但返回 true,false,TypeError
Reflect.deleteProperty(obj,'a') //false
// Reflect.get(obj,'attributeName'[,receiver]) //取得值
Reflect.get(obj,'a') //40
// Reflect.getOwnPropertyDescriptor(obj,'attributeName') //如同 Object.getOwnPropertyDescriptor ,但可能拋出TypeError
Reflect.getOwnPropertyDescriptor('string','s') //TypeError
Object.getOwnPropertyDescriptor('string','s') //undefined
// Reflect.getPrototypeOf(obj) //如同 Object.getPrototypeOf ,但可能拋出TypeError
Reflect.getPrototypeOf(obj) //{ hello: [Function: hello] }
Reflect.getPrototypeOf(1) //TypeError
// Reflect.has(obj,'attributeName') //如同 'in' 符號
Reflect.has(obj,'a')==='a' in obj //true
// Reflect.isExtensible(obj) //如同Object.isExtensible ,但可能拋出TypeError
Reflect.isExtensible(1) //TypeError
Object.isExtensible(1) //false
// Reflect.ownKeys(obj) //如同Object.keys 不受enumerable影響,symbol也會show
Reflect.ownKeys(obj) //[ 'a', 'b', 'c', Symbol(symbol string) ]
Object.keys(obj) //[ 'a', 'c']
// Reflect.preventExtensions(obj) //如同Object.preventExtensions 返回true,false,TypeError
Reflect.preventExtensions(obj) //true
Object.preventExtensions(obj) //obj
// Reflect.set(obj, 'attributeName', value [, receiver]) //如同 '=' 符號 返回true,false,TypeError
Reflect.set(obj, 'a', 10) //false
// Reflect.setPrototypeOf(obj, 'attributeName') //如同 Object.setPrototypeOf 返回 true,false,TypeError
Reflect.setPrototypeOf(1, {}) //TypeError
Object.setPrototypeOf(1, {}) //1
// Proxy 類似hook 的概念
var proxy= new Proxy(obj, {
get: function (target, key, receiver) {
console.log("target:", target)
console.log("key:", key)
console.log("receiver is this proxy:", receiver===proxy) //true
console.log("Reflect:", Reflect);
return Reflect.get(target, key, receiver); //overwrite get,if no return no Reflect then return undefined
},
set: function (target, key, value, receiver) {
console.log("target:", target)
console.log("key:", key)
console.log("value:", value)
console.log("receiver is this proxy:", receiver===proxy)
console.log("Reflect:", Reflect);
return Reflect.set(target, key, value, receiver); //overwrite set,if no Reflect then set invalid
}
})
/* 還可用在
// //getPrototypeOf
// //setPrototypeOf
// //isExtensible
// //preventExtensions
// //getOwnPropertyDescriptor
// //defineProperty
// //has
// //deleteProperty
// //ownKeys
// //apply
// //construct
*/
// promise
new Promise (function (resolve, reject) {
resolve('return1'); //如同 return
reject('error1'); //如同 throw
}).then(function(arg) { // arg == 'return1'
console.log(arg);
throw('error2');
return 'return2';
}).catch(function(err) { // err == 'error2'
console.log(err);
})
// return1
// error2
// async
function callme1(time) {
return Math.random()
}
function callme2(time) {
return new Promise(function (resolve, reject) {
setTimeout(function(){
resolve(Math.random())
},time)
})
}
async function asyncFunc (time) {
result=await callme1(time)
console.log(result) // 隨機值
console.log('ok1')
result=await callme2(time) // 返回Promise所得到的隨機值 而非Promise物件
console.log('typeof:',typeof(result))
console.log(result)
console.log('ok2')
return "hello world"
}
asy=asyncFunc(3000)
console.log(typeof(asy)) // async 函數返回 Promise物件
asy.then((result)=>{console.log(result)}) // hello world
// generator
result=[]
function * generator(a) {
console.log('===start===')
console.log('a:',a)
b = yield 1
console.log('b:',b)
c = yield 2
console.log('c:',c)
}
gen=generator("this is a") // 代入a變數,返回generator物件,尚未開始執行
console.log('===let go===')
result.push( gen.next() ) // output:'===start===' arg:代什麼都無效果
result.push( gen.next("this is b") ) // 代入b變數
result.push( gen.next("this is c") ) // 代入c變數
console.log(result) // [{ value: 1, done: false }, { value: 2, done: false }, { value: undefined, done: true }]
// encodeURI(string) // encode ASCII、number、~!()*' . no encode
encodeURI(str1) // 'http://www.google.tw/search?q=%E4%B8%AD%E6%96%87'
// encodeURIComponent(string) // encode ASCII、number、~!()*'@#$&=:/,;?+ no encode
str2=encodeURIComponent(str1) // 'http%3A%2F%2Fwww.google.tw%2Fsearch%3Fq%3D%E4%B8%AD%E6%96%87'
// decodeURI(string) // decode ASCII、number、~!()*' no decode
decodeURI(str2) // 'http%3A%2F%2Fwww.google.tw%2Fsearch%3Fq%3D中文'
// decodeURIComponent(string) // decode ASCII、number、~!()*'@#$&=:/,;?+ no decode
decodeURIComponent(str2) // 'http://www.google.tw/search?q=中文'
//string.padStart(length [, padding]) //string 使用 padding 填充字串開頭使 string.lenght==length, 預設padding==' '
str1.padStart(39) //' http://www.google.tw/search?q=中文'
str1.padStart(39,'h') // 'hhhhhhhhttp://www.google.tw/search?q=中文'
str1.padStart(39,'he') // 'hehehehhttp://www.google.tw/search?q=中文'
// string.padEnd(length [, padding]) //string 使用 padding 填充字串末端使 string.lenght==length, 預設padding==' '
str1.padEnd(39) // ' http://www.google.tw/search?q=中文'
str1.padEnd(39,'h') // 'http://www.google.tw/search?q=中文hhhhhhh'
str1.padEnd(39,'he') // 'http://www.google.tw/search?q=中文heheheh'
// [obj1,obj2,obj3,] // 陣列末端','不報錯
[{a:1},{b:2},{c:3},] // [ { a: 1 }, { b: 2 }, { c: 3 } ]
// [..."string"] // 'string'.split('')
[..."string"] // ["s","t","r","i","n","g"]
// [...[obj1,obj2,obj3]] // [obj1,obj2,obj3]
[...[{a:1},{b:2},{c:3}]] // [ { a: 1 }, { b: 2 }, { c: 3 } ]
//ArrayBuffer
ab=new ArrayBuffer(12)
//new [Uint](8|16|32|8)Array(obj: ArrayBuffer)
u8a=new Uint8Array(ab)
u8a[0]=72
u16a=new Uint16Array(u8a.buffer)
u16a[1]=27756
dv=new DataView(u16a.buffer)
dv.setUint16(4,8303,true) //littleEnd
dv.setUint32(6,1466921580)
i16a=new Int16Array(ab)
i16a[5]=8548
i8a=new Int8Array(ab)
i8a[1]=101
str=String.fromCharCode.apply("", u8a)
buf=new Uint8Array([].map.call(str,function(c){return c.charCodeAt(0)}) )
@GHolk
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GHolk commented Sep 24, 2017

js 新語法也太多了 @@

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