splice() might be able to help out, though how much depends on whether the copying really needs to overlap or not. There's some benchmarks at: http://jsperf.c

splice() might be able to help out, though how much depends on whether the copying really needs to overlap or not. There's some benchmarks at: http://jsperf.com/backreference-copy http://jsperf.com/backreference-copy I couldn't actually get Safari to complete; FF 4.01 is fastest by a long way.