JS code snippets http://dmitrysoshnikov.com/ecmascript/javascript-the-core-2nd-edition/

snippets.js

function doubleAfter2Seconds(x) {
    return new Promise((resolve, reject) => {
        resolve(x * 2)
    }, 2000)
}

async function addAsync(x) {
    const a = doubleAfter2Seconds(10);
    const b = doubleAfter2Seconds(20);
    const c = doubleAfter2Seconds(30);
    return x + (await a) + (await b) + (await c);
}

addAsync(10).then(e => console.log(e))


function foo() {
  return () => {
    return () => {
      return () => {
        console.log("id:", this.id);
      };
    };
  };
}

var f = foo.call({id: 1});

var t1 = f.call({id: 2})()();
var t2 = f().call({id: 3})();
var t3 = f()().call({id: 4});
// from [关于箭头函数this的理解几乎完全是错误的](https://github.com/ruanyf/es6tutorial/issues/150)

// 箭头函数与普通函数的差异， 箭头函数的执行环境是， 创建箭头函数所在的对象(lexical scoping, 从源代码中即可知道环境是什么， global 环境， 还是其他对象）

function a(x200){
    return (x300) =>  {
        return (x400) => {
            return this.x;
        }
    }
}

function a(x200){
    return function(x300) {
        return (x400) => {
            return this.x;
        }
    }
}

function a(){
    return function(){
        return function(){
            return this.x;
        }
    }
}

x = 100
console.log(a.call({x: 200}).call({x: 300}).call({x: 400}))

const R = require('ramda')

const sum = (args) => R.reduce((x,y) => x + y, 0, args)
const gte10 = R.gte(R.__, 10)
const lte20 = R.lte(R.__, 20)
const range10to20 = R.both(gte10, lte20)
constructMsg = (v) => `the magic number is: ${v}`

const sumOnlyFavorite = R.compose(
    sum,
    R.filter(range10to20)
)

const printMagicNumber = R.pipe(
    sumOnlyFavorite,
    constructMsg
)

const numbers = [4,10,0,27,42,17,15,-6,58];
printMagicNumber(numbers)

使用 ramda 重写 https://github.com/getify/Functional-Light-JS/blob/master/manuscript/ch1.md 中的例子