正则新增特性

构造函数的变化 正则方法的扩展 u 修饰符 y 修饰符 s 修饰符

{
  // es5
  let regex = new RegExp('xyz', 'i')
  let regex2 = new RegExp(/xyz/i)

  console.log(regex.test('xyz123'), regex2.test('xyz123')) // true true

  // es6
  let regex3 = new RegExp(/xyz/gi, 'i')
  console.log(regex3.flags) // i
  // ES6为正则表达式新增了flags属性，会返回正则表达式的修饰符。
}

{
  let s = 'bbb_bb_b'
  let a1 = /b+/g
  let a2 = /b+/y
  console.log('one', a1.exec(s), a2.exec(s))
  // one ["bbb", index: 0, input: "bbb_bb_b", groups: undefined]  ["bbb", index: 0, input: "bbb_bb_b", groups: undefined]
  console.log('two', a1.exec(s), a2.exec(s))
  // two ["bb", index: 4, input: "bbb_bb_b", groups: undefined] null
  console.log(a1.sticky, a2.sticky) // false true
}

{
  console.log('u-1', /^\uD83D/.test('\uD83D\uDC2A')) // u-1 true
  console.log('u-2', /^\uD83D/u.test('\uD83D\uDC2A')) // u-2 false

  console.log(/\u{61}/.test('a')) // false
  console.log(/\u{61}/u.test('a')) // true

  console.log(`\u{20BB7}`) // 𠮷

  let s = '𠮷'

  console.log('u-1', /^.$/.test(s)) // u-1 false
  console.log('u-2', /^.$/u.test(s)) // u-2 true

  console.log('test-1', /𠮷{2}/.test('𠮷𠮷')) // test-1 false
  console.log('test-2', /𠮷{2}/u.test('𠮷𠮷')) // test-2 true
}