JSTests/test262/test/language/expressions/compound-assignment/S11.13.2_A4.4_T2.8.js

// Copyright 2009 the Sputnik authors.  All rights reserved.
// This code is governed by the BSD license found in the LICENSE file.

/*---
info: The production x += y is the same as x = x + y
es5id: 11.13.2_A4.4_T2.8
description: >
    Type(x) is different from Type(y) and both types vary between
    String (primitive or object) and Undefined
---*/

var x;

//CHECK#1
x = "1";
x += undefined;
if (x !== "1undefined") {
  throw new Test262Error('#1: x = "1"; x += undefined; x === "1undefined". Actual: ' + (x));
}

//CHECK#2
x = undefined;
x += "1";
if (x !== "undefined1") {
  throw new Test262Error('#2: x = undefined; x += "1"; x === "undefined1". Actual: ' + (x));
}

//CHECK#3
x = new String("1");
x += undefined;
if (x !== "1undefined") {
  throw new Test262Error('#3: x = new String("1"); x += undefined; x === "1undefined". Actual: ' + (x));
}

//CHECK#4
x = undefined;
x += new String("1");
if (x !== "undefined1") {
  throw new Test262Error('#4: x = undefined; x += new String("1"); x === "undefined1". Actual: ' + (x));
}