Pointfree Javascript: Pointfree編程風格

過程式編碼是這樣的：

var getAdminUsers = users => {
  var emails = []
  users.forEach(v=>{
    v.role==='admin' && emails.push(v.email)
  })
  return emails
}

易讀的方式重寫：

let getAdminEmails = users =>
    users
      .filter(u => u.role === 'admin')
      .map(u => u.email);

Pointfree ：

var prop = p => x => x[p];

var map = f => list =>
  list.map(f);

var propEq = v => p => obj =>
  prop(p)(obj) === v;

var filter = f => list =>
  list.filter(f);

pipe函數：

const pipe = (...args) => x=> args.reduce((ini, fn)=> fn(ini), x)

下面開始放大招：

var getAdminEmails = pipe(
　　filter(
    　　propEq('admin')('role')),
　　map( prop('email')));

之後就能夠這樣愉快地調用了：

var arr = [{role: 'admin', email: 'suibdkhgigh'}]
getAdminEmails(arr) //["suibdkhgigh"]