JSDeferred の loop 関数は軽かろうが重かろうか一回ずつ setTimeout はさむんで効率わるいので、for ループと loop 関数の間ぐらいの関数をてきとうに書いてみた。

	function aloop (n, f) {
		var i   = 0;
		var end = new Object;
		var ret = null;
		return Deferred.next(function () {
			var t = (new Date()).getTime();
			try {
				do {
					ret = f(i)
					i++;
					if (i > n) throw end;
				} while ((new Date()).getTime() - t < 100)
				log("Devided: " + ((new Date()).getTime() - t) + "msec.");
				return Deferred.call(arguments.callee);
			} catch (e) {
				if (e == end) {
					log("End");
					return ret;
				} else {
					throw e;
				}
			}
		});
	}

	aloop(100, function (n, o) {
		var dummy = 0;
		log(n);
		for (var i = 0; i < n * n * n; i++) {
			dummy++;
		}
	});

関数一回の処理に 100msec 以上かかってしまったら、一度ブラウザに処理をかえす。

この例だとこんなふうになります

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http://lowreal.net/Test: 0
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http://lowreal.net/Test: Devided: 109msec.
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http://lowreal.net/Test: Devided: 116msec.
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http://lowreal.net/Test: Devided: 109msec.
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http://lowreal.net/Test: Devided: 113msec.
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http://lowreal.net/Test: Devided: 103msec.
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http://lowreal.net/Test: Devided: 119msec.
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http://lowreal.net/Test: Devided: 137msec.
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http://lowreal.net/Test: Devided: 103msec.
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http://lowreal.net/Test: Devided: 112msec.
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http://lowreal.net/Test: Devided: 122msec.
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http://lowreal.net/Test: Devided: 133msec.
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http://lowreal.net/Test: Devided: 144msec.
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http://lowreal.net/Test: Devided: 158msec.
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http://lowreal.net/Test: Devided: 168msec.
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http://lowreal.net/Test: Devided: 182msec.
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http://lowreal.net/Test: Devided: 194msec.
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http://lowreal.net/Test: Devided: 103msec.
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http://lowreal.net/Test: Devided: 106msec.
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http://lowreal.net/Test: Devided: 110msec.
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http://lowreal.net/Test: Devided: 114msec.
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http://lowreal.net/Test: Devided: 118msec.
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http://lowreal.net/Test: Devided: 122msec.
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http://lowreal.net/Test: Devided: 144msec.
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http://lowreal.net/Test: Devided: 148msec.
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http://lowreal.net/Test: Devided: 153msec.
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http://lowreal.net/Test: Devided: 158msec.
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http://lowreal.net/Test: Devided: 166msec.
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http://lowreal.net/Test: Devided: 171msec.
http://lowreal.net/Test: 100
http://lowreal.net/Test: End

実際つかうならハードコードされてるところをましにしたりしないといけないかな。