I mean instead of [].concat(arr1,arr2,arr3) use http://www.espruino.com/Reference#l_ArrayBufferView_set:
[].concat(arr1,arr2,arr3)
var tmp = new Uint8ClampedArray(leds*3); // preallocate this tmp.set(arr1,0); tmp.set(arr2,leds); tmp.set(arr2,leds*2);
@Gordon started
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I mean instead of
[].concat(arr1,arr2,arr3)
use http://www.espruino.com/Reference#l_ArrayBufferView_set: