gistfile1.js

// NB: this micro-benchmark is stupid in a sense that all loops can be potentially optimized away
// but it's only purpose is to show that variable accesses become slower when eval is in the same scope.
//    -- Vyacheslav Egorov

function foo () {
    var j = 0;
    for (var i = 0; i < 1e7; i++) j = i;
    for (var i = 0; i < 1e7; i++) j = i;
    for (var i = 0; i < 1e7; i++) j = i;
    return j;
}

function bar () {
    var j = 0;
    for (var i = 0; i < 1e7; i++) j = i;
    for (var i = 0; i < 1e7; i++) j = i;
    for (var i = 0; i < 1e7; i++) j = i;
    eval("");
    return j;
}

function baz () {
    function baz1() {
	var j = 0;
	for (var i = 0; i < 1e7; i++) j = i;
	for (var i = 0; i < 1e7; i++) j = i;
	for (var i = 0; i < 1e7; i++) j = i;
        return j;
    }
    eval("");
    return baz1();
}

function qux () {
    var j = 0;
    function qux1() {
	for (var i = 0; i < 1e7; i++) j = i;
	for (var i = 0; i < 1e7; i++) j = i;
	for (var i = 0; i < 1e7; i++) j = i;
    }
    qux1();
    return j;
}

function quux () {
    var j = 0;
    function quux1() {
	for (var i = 0; i < 1e7; i++) j = i;
	for (var i = 0; i < 1e7; i++) j = i;
	for (var i = 0; i < 1e7; i++) j = i;
    }
    eval("");
    quux1();
    return j;
}



function m (f) {
    var s = Date.now();
    f();
    print(Date.now() - s);    
}

m(foo);
m(bar);
m(baz);
m(qux);
m(quux);