fast/js/eval-keyword-vs-function.html

<p>
This page verifies that eval has two meanings:
<ol>
    <li>An operator: executes a script in local scope with the local scope's variable object and "this" object.</li>
    <li>A global function: executes a script in global scope with the global scope's variable object and "this" object.</li>
</ol>
Meaning #2 should remain constant even if the global eval function is copied
into a global variable ("globalEval") or a local variable ("localEval").
</p>
<p>If the test passes, you'll see a series of pass messages below.</p>
<hr>
<pre id="console"></pre>

<script>
if (window.testRunner)
    testRunner.dumpAsText();
    
var globalEval = eval;

function log(s)
{
    document.getElementById("console").appendChild(document.createTextNode(s + "\n"));
}

function shouldBe(aDescription, a, b)
{
    if (a === b) {
        log("PASS: " + aDescription + " should be " + b + " and is.");
    } else {
        log("FAIL: " + aDescription + " should be " + b + " but instead is " + a + ".");
    }
}

function testGetX()
{
    var x = 1;
    var localEval = window.eval;
    
    window.x = 0;

    shouldBe('eval("x")', eval("x"), 1);

    shouldBe('window.eval("x")', window.eval("x"), 0);
    shouldBe('globalEval("x")', globalEval("x"), 0);
    shouldBe('localEval("x")', localEval("x"), 0);

    // Per ES5 15.1.2.11 & 10.2.2.1 any reference that hits an enviromment record (i.e. does not have a base)
    // and has a reference name of "eval" is treated as a direct eval - the assignment to a var makes no difference.
    shouldBe('(function() { var eval = window.eval; return eval("x"); })()', (function() { var eval = window.eval; return eval("x"); })(), 1);
}

function testVarY()
{
    var localEval = window.eval;

    shouldBe('eval("var y; \"y\" in window")', eval("var y; \"y\" in window"), false);
    delete window.y;
    
    shouldBe('window.eval("var y; \"y\" in window")', window.eval("var y; \"y\" in window"), true);
    delete window.y;

    shouldBe('globalEval("var y; \"y\" in window")', globalEval("var y; \"y\" in window"), true);
    delete window.y;

    shouldBe('localEval("var y; \"y\" in window")', localEval("var y; \"y\" in window"), true);
    delete window.y;
    
    // Per ES5 15.1.2.11 & 10.2.2.1 any reference that hits an enviromment record (i.e. does not have a base)
    // and has a reference name of "eval" is treated as a direct eval - the assignment to a var makes no difference.
    shouldBe('(function() { var eval = window.eval; return eval("var y; \"y\" in window"); })()', (function() { var eval = window.eval; return eval("var y; \"y\" in window"); })(), false);
}

function testSetZ()
{
    var z = 0;
    window.z = 0;
    var localEval = window.eval;

    shouldBe('eval("z = 1; window.z")', eval("z = 1; window.z"), 0);

    shouldBe('window.eval("z = 2; window.z")', window.eval("z = 2; window.z"), 2);
    
    shouldBe('globalEval("z = 3; window.z")', globalEval("z = 3; window.z"), 3);

    shouldBe('localEval("z = 4; window.z")', localEval("z = 4; window.z"), 4);

    // Per ES5 15.1.2.11 & 10.2.2.1 any reference that hits an enviromment record (i.e. does not have a base)
    // and has a reference name of "eval" is treated as a direct eval - the assignment to a var makes no difference.
    shouldBe('(function() { var eval = window.eval; return eval("z = 5; window.z"); })()', (function() { var eval = window.eval; return eval("z = 5; window.z"); })(), 4);
}

function testThis()
{
    var localEval = window.eval;

    shouldBe('eval("this")', eval("this"), this);
    shouldBe('window.eval("this")', window.eval("this"), window);
    shouldBe('globalEval("this")', globalEval("this"), window);
    shouldBe('localEval("this")', localEval("this"), window);
    shouldBe('(function() { var eval = window.eval; return eval("this"); })()', (function() { var eval = window.eval; return eval("this"); })(), window);
}

log("\n----- Scope Chain for Getters: -----\n");
testGetX();
log("\n----- Variable Object: -----\n");
testVarY();
log("\n----- Scope Chain for Setters: -----\n");
testSetZ();
log("\n----- This Object: -----\n");
testThis.call({ toString: function() { return "[\"this\" object passed to .call()]"; } });
</script>