ts/js context problem on replace (resolves b bind, but fact)

class Cls {
  constructor() {

  }
  replacer () {
    console.log(this)
    return '6'
  }
  func(){
    console.log(JSON.stringify(this))
    var r = '123456'.replace(/1/g, this.replacer)
    console.log(r)
  }
}


var ex = new Cls()

ex.replacer()
ex.func()