// Copyright 2016 the V8 project authors. All rights reserved.// Use of this source code is governed by a BSD-style license that can be// found in the LICENSE file.// lastIndex is set only for global or sticky RegExps. On failure to find// a match, it is set to 0. If a set fails, then it acts as if in strict mode// and throws.varre=/x/g;Object.defineProperty(re,'lastIndex',{writable:false});assertThrows(()=>re.exec(""),TypeError);assertThrows(()=>re.exec("x"),TypeError);varre=/x/y;Object.defineProperty(re,'lastIndex',{writable:false});assertThrows(()=>re.exec(""),TypeError);assertThrows(()=>re.exec("x"),TypeError);varre=/x/;Object.defineProperty(re,'lastIndex',{writable:false});assertEquals(null,re.exec(""));assertEquals(["x"],re.exec("x"));