RegExp.prototype[Symbol.replace]()

class RegExp1 extends RegExp {
  [Symbol.replace](str) {
    return RegExp.prototype[Symbol.replace].call(this, str, "#!@?");
  }
}

console.log("football".replace(new RegExp1("foo")));
// Expected output: "#!@?tball"

regexp[Symbol.replace](str, replacement)

"abc".replace(/a/, "A");

/a/[Symbol.replace]("abc", "A");

var re = /-/g;
var str = "2016-01-01";
var newstr = re[Symbol.replace](str, ".");
console.log(newstr); // 2016.01.01

class MyRegExp extends RegExp {
  constructor(pattern, flags, count) {
    super(pattern, flags);
    this.count = count;
  }
  [Symbol.replace](str, replacement) {
    // 执行 [Symbol.replace]() |count| 次。
    var result = str;
    for (var i = 0; i < this.count; i++) {
      result = RegExp.prototype[Symbol.replace].call(this, result, replacement);
    }
    return result;
  }
}

var re = new MyRegExp("\\d", "", 3);
var str = "01234567";
var newstr = str.replace(re, "#"); // String.prototype.replace 调用 re[Symbol.replace]()。
console.log(newstr); // ###34567