=> ES8 2017
'1'.padStart(2, '*') // '*1'
'1'.padEnd(2, '*') // '1*'
'1'.padStart(6, '*#') // '*#*#*1'
=> ES8 2017
let obj = {
name: 'james',
age: 22,
sex: 1
}
Object.defineProperty(obj, 'name', {enumerable: false})
console.log(Object.keys(obj)) // 会没有name