ltgt

What is ltgt?

The 'ltgt' npm package provides utility functions for comparing values with less than, greater than, less than or equal to, and greater than or equal to operations. It is particularly useful for range queries and sorting operations.

What are ltgt's main functionalities?

Less Than Comparison

This feature allows you to compare if one value is less than another. In this example, it checks if 3 is less than 5.

const ltgt = require('ltgt');
const result = ltgt.compare(3, 5, '<');
console.log(result); // true

Greater Than Comparison

This feature allows you to compare if one value is greater than another. In this example, it checks if 7 is greater than 5.

const ltgt = require('ltgt');
const result = ltgt.compare(7, 5, '>');
console.log(result); // true

Range Query

This feature allows you to check if a value falls within a specified range. In this example, it checks if 5 is within the range of 1 to 10.

const ltgt = require('ltgt');
const range = { start: 1, end: 10 };
const result = ltgt.contains(range, 5);
console.log(result); // true

Less Than or Equal To Comparison

This feature allows you to compare if one value is less than or equal to another. In this example, it checks if 5 is less than or equal to 5.

const ltgt = require('ltgt');
const result = ltgt.compare(5, 5, '<=');
console.log(result); // true

Greater Than or Equal To Comparison

This feature allows you to compare if one value is greater than or equal to another. In this example, it checks if 5 is greater than or equal to 5.

const ltgt = require('ltgt');
const result = ltgt.compare(5, 5, '>=');
console.log(result); // true

Other packages similar to ltgt

lodash

Lodash is a modern JavaScript utility library delivering modularity, performance, and extras. It provides a wide range of utility functions for common programming tasks, including comparison operations. Compared to 'ltgt', Lodash offers a broader set of functionalities beyond just comparison operations.

underscore

Underscore is a JavaScript library that provides a whole mess of useful functional programming helpers without extending any built-in objects. It includes functions for comparison and range queries, similar to 'ltgt', but also offers a wide array of other utility functions.

ramda

Ramda is a practical functional library for JavaScript programmers. It makes it easy to create functional pipelines and includes a variety of utility functions, including comparison operations. Ramda focuses on functional programming paradigms, which can be more complex but also more powerful compared to 'ltgt'.

README

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.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