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README.md
ltgt
implement correct ranges for level-*
example
var ltgt = require('ltgt')
ltgt.start(range) //the start of the range
ltgt.end(range) //the end of the range
//returns the lower/upper bound, whether it's inclusive or not.
ltgt.lowerBound(range)
ltgt.upperBound(range)
ltgt.lt(range)
ltgt.gt(range)
ltgt.lte(range)
ltgt.gte(range)
//return wether this is a reversed order
//(this is significant for start/end ranges
ltgt.reverse(range)
var filter = ltgt.filter(range)
filter(key) == true //if key contained in range.
ltgt.contains(range, key)
ways to specify ranges
there have been a variety of ways to specify ranges in level-*. this module supports them all.
gt/gte, lt/lte
specify a range between a lower bound (gt, gte) and an upper bound (lt, lte)
if gte
and gt
is undefined, read from the start of the database,
if lte
and lt
is undefined, read until the end of the database,
min, max
legacy level-sublevel style,
synonym for gte
, lte
.
start, end, reverse
legacy levelup style.
The range is from start
-> end
, start
does not specify the lowest
record, instead it specifies the first record to be read. However,
reverse
must also be passed correctly. This is way to specify a range is
confusing if you need to read in reverse,
so it's strongly recommended to use gt/gte,lt/lte
.
If reverse
is true
,
start
must be undefined
or less than end
,
unless end
is undefined
.
if reverse
is false
end
must be undefined
or greater than start
,
unless start
is undefined
.
if start is undefined, read from the first record in the database if end is undefined read until the last record in the database.
api
ltgt.contains(range, key, compare)
using the provided compare method, return true
if key
is within range
. compare defaults to ltgt.compare
ltgt.filter(range, compare)
return a function that returns true if it's argument is within range.
can be passed to Array.filter
[1,2,3,4,5].filter(ltgt.filter({gt: 2, lte: 4})
// => [3, 4]
ltgt.lowerBound(range)
return the lower bound of range
.
Incase the lower bound is specified with gt
,
check ltgt.lowerBoundExclusive
ltgt.upperBound(range)
return the upperBound of range
.
Incase the upper bound is specified with gt
,
check ltgt.upperBoundExclusive
ltgt.lowerBoundExclusive(range)
return true if upper bound is exclusive.
ltgt.upperBoundExclusive(range)
return true if lower bound is exclusive.
ltgt.start(range, default)
The start of the range. This takes into account direction (reverse)
If a start
is not provided, default
is used.
ltgt.end(range, default)
The end of the range. This takes into account direction (reverse)
If a end
is not provided, default
is used.
ltgt.startInclusive(range)
returns true if the range should start at the exact value returned
by start(range)
otherwise, it should skip one input.
ltgt.endInclusive(range)
returns true if the range should include the exact value returned
by end(range)
otherwise, it should end on that value.
ltgt.toLtgt(range, _range, map, lowerBound, upperBound)
convert a range to a new ltgt range. _range
is the object to return - if you want to mutate range
call ltgt.toLtgt(range, range, map)
map
gets called on each key in the range, and wether it's an upper or lower bound -
so can be used as an encode function.
map(value, isUpperBound)
if isUpperBound
is false, this is the lower bound.
License
MIT