#### async 自動執行的generator + promise ``` function *main() { var res = yield step1(); res = yield step2(res); res = yield Promise.all([step3a(res), step3b(res)]); yield step4(res); } run(main).then(() => console.log('succeed'), () => console.log(err)); //async async function main() { var res = await step1(); res = await step2(res); res = await Promise.all([step3a(res), step3b(res)]); await step4(res); } main().then(() => console.log('succeed'), () => console.log(err)) //async函數有一個沒有解決的問題，這也是它的缺點，就是無法從外部取消正在運行的async，你只能等到它運行結束然后操作它返給你的promise ``` #### Object.observe（已廢棄） ``` var obj = {a: 1, b: 2}; Object.observe( obj, function(changes) { for(var change of changes) { console.log(change); } }, ["add", "update", "delete"] ); obj.c = 3; //{name: "c", object: obj, type: "add"} obj.a = 42; //{name: "a", object: obj, type: "update", oldValue: 1} delete obj.b; //{name: "b", object: obj, type: "delete", oldValue: 2} ``` ``` var obj = {a: 1, b: 2}; Object.observe(obj, function observer(changes) { for(var change of changes) { if(change.type == "setPrototype") { Object.unobserve(change.object, observer); break; } } }) ``` #### 冪運算 ``` a ** 4; //Math.pow(a, 4) a **= 3; //a = Math.pow(a, 3) ``` #### 對象屬性與... ``` o3 = {...o1, ...o2, {a: 1}}; //clear var o1 = {b: 2, c: 3, d: 4} var {b, ...o2} = o1; b; //2 o2; //{c: 3, d: 4} ``` #### Array.includes ``` var vals = ["foo", "bar", 42, "baz"]; //查找42的話需要用indexOf，但是indexOf會返回-1或者大于等于0的值，不利于轉換成bool //因此用 !!(~vals.indexOf(42)); //true (~a=-(a+1)) //es7 vals.includes(42); //true ```