Have you considered JSON?
var multi = [
[1,2,3],
[4,5,6,7],
[8,9,10]
];
alert(multi[0][2]); // '3'
alert(multi[1][3]); // '7'
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Give a man a match, he'll be warm for a minute. But light him on fire, and he'll be warm for the rest of his life.