How to append new pair of values to array?

Hello, may I please ask for help?

I have hand defined as polygon in array. Now I want to create another array were all values are off-set to draw shadow first. What would be the correct syntax and command to iterate through original array of pairs and create new one? I have following script, but core statement missing...

var dc_offset = 3;
var mhvg = [[6,0],[6,-30],[-6,-30],[-6,0]];         // original hand
var mhvg_with_offset; // shadow - new two-dimensional array with original pairs offseted

for (var i = 0; i < mhvg.size(); ++i) {
// new pair in array mhvg_with_offset = [[mhvg[i,0]+dc_offset,mhvg[i,1]+dc_offset];
}

Thank you very much, Jan