| /* -*- tab-width: 2; indent-tabs-mode: nil; js-indent-level: 2 -*- */ |
| /* This Source Code Form is subject to the terms of the Mozilla Public |
| * License, v. 2.0. If a copy of the MPL was not distributed with this |
| * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ |
| |
| |
| /** |
| File Name: 12.10-1.js |
| ECMA Section: 12.10 The with statement |
| Description: |
| WithStatement : |
| with ( Expression ) Statement |
| |
| The with statement adds a computed object to the front of the scope chain |
| of the current execution context, then executes a statement with this |
| augmented scope chain, then restores the scope chain. |
| |
| Semantics |
| |
| The production WithStatement : with ( Expression ) Statement is evaluated |
| as follows: |
| 1. Evaluate Expression. |
| 2. Call GetValue(Result(1)). |
| 3. Call ToObject(Result(2)). |
| 4. Add Result(3) to the front of the scope chain. |
| 5. Evaluate Statement using the augmented scope chain from step 4. |
| 6. Remove Result(3) from the front of the scope chain. |
| 7. Return Result(5). |
| |
| Discussion |
| Note that no matter how control leaves the embedded Statement, whether |
| normally or by some form of abrupt completion, the scope chain is always |
| restored to its former state. |
| |
| Author: christine@netscape.com |
| Date: 12 november 1997 |
| */ |
| |
| var SECTION = "12.10-1"; |
| var VERSION = "ECMA_1"; |
| startTest(); |
| var TITLE = "The with statement"; |
| |
| writeHeaderToLog( SECTION + " "+ TITLE); |
| |
| |
| // although the scope chain changes, the this value is immutable for a given |
| // execution context. |
| |
| new TestCase( SECTION, |
| "with( new Number() ) { this +'' }", |
| GLOBAL, |
| eval("with( new Number() ) { this +'' }") ); |
| |
| // the object's functions and properties should override those of the |
| // global object. |
| |
| new TestCase( |
| SECTION, |
| "var MYOB = new WithObject(true); with (MYOB) { parseInt() }", |
| true, |
| eval("var MYOB = new WithObject(true); with (MYOB) { parseInt() }") ); |
| |
| new TestCase( |
| SECTION, |
| "var MYOB = new WithObject(false); with (MYOB) { NaN }", |
| false, |
| eval("var MYOB = new WithObject(false); with (MYOB) { NaN }") ); |
| |
| new TestCase( |
| SECTION, |
| "var MYOB = new WithObject(NaN); with (MYOB) { Infinity }", |
| Number.NaN, |
| eval("var MYOB = new WithObject(NaN); with (MYOB) { Infinity }") ); |
| |
| new TestCase( |
| SECTION, |
| "var MYOB = new WithObject(false); with (MYOB) { }; Infinity", |
| Number.POSITIVE_INFINITY, |
| eval("var MYOB = new WithObject(false); with (MYOB) { }; Infinity") ); |
| |
| |
| new TestCase( |
| SECTION, |
| "var MYOB = new WithObject(0); with (MYOB) { delete Infinity; Infinity }", |
| Number.POSITIVE_INFINITY, |
| eval("var MYOB = new WithObject(0); with (MYOB) { delete Infinity; Infinity }") ); |
| |
| // let us leave the with block via a break. |
| |
| new TestCase( |
| SECTION, |
| "var MYOB = new WithObject(0); while (true) { with (MYOB) { Infinity; break; } } Infinity", |
| Number.POSITIVE_INFINITY, |
| eval("var MYOB = new WithObject(0); while (true) { with (MYOB) { Infinity; break; } } Infinity") ); |
| |
| |
| test(); |
| |
| function WithObject( value ) { |
| this.prop1 = 1; |
| this.prop2 = new Boolean(true); |
| this.prop3 = "a string"; |
| this.value = value; |
| |
| // now we will override global functions |
| |
| this.parseInt = new Function( "return this.value" ); |
| this.NaN = value; |
| this.Infinity = value; |
| this.unescape = new Function( "return this.value" ); |
| this.escape = new Function( "return this.value" ); |
| this.eval = new Function( "return this.value" ); |
| this.parseFloat = new Function( "return this.value" ); |
| this.isNaN = new Function( "return this.value" ); |
| this.isFinite = new Function( "return this.value" ); |
| } |