nl_tokens: This function implements the optimized splice implementation that can use special array operations to handle sparse arrays in a sensible fashion .
pl_tokens: function SparseSlice ( array , start_i , del_count , len , deleted_elements ) { // Move deleted elements to a new array (the return value from splice). var indices = % GetArrayKeys ( array , start_i + del_count ) ; if ( IS_NUMBER ( indices ) ) { var limit = indices ; for ( var i = start_i ; i < limit ; ++ i ) { var current = array [ i ] ; if ( ! IS_UNDEFINED ( current ) || i in array ) { % CreateDataProperty ( deleted_elements , i - start_i , current ) ; } } } else { var length = indices . length ; for ( var k = 0 ; k < length ; ++ k ) { var key = indices [ k ] ; if ( key >= start_i ) { var current = array [ key ] ; if ( ! IS_UNDEFINED ( current ) || key in array ) { % CreateDataProperty ( deleted_elements , <mask> - start_i , current ) ; } } } } }