1function FindProxyForURL(url, host){ 2 let re = /x/y; 3 let cnt = 0; 4 let str = re[Symbol.replace]("x", { 5 toString: () => { 6 cnt++; 7 if (cnt == 2) { 8 re.lastIndex = {valueOf: () => { 9 re.x = 42; 10 return 0; 11 }}; 12 } 13 return 'y$'; 14 } 15 }); 16 if (str != "y$") { 17 throw "regex mutated"; 18 return "FAIL"; 19 } 20 return "DIRECT"; 21}