♊ join-table
Fast, mutable collection of many-to-many pairs of values.
A JoinTable instance is effectively a table of two columns ('left' and 'right'). It's similar to an ES2015 Set in that a given left-right combination can only occur once in a table.
Usage
; const table = ; table;table;table; table; // truetable; // truetable; // true table; // falsetable; // false (wrong order)table; // false (strings !== integers) table; // Set {'bar', 'baz'}table; // Set {'foo'}
API
add(left, right)
Adds a join and returns the table. Has no effect if this exact join already exists.
remove(left, right)
Removes a join and returns the table. Has no effect if this exact join does not exist.
has(left, right)
Checks if the join exists and returns true
or false
.
clear()
Empties the table.
getRightsFor(left)
Returns the Set of ‘right’ values that are joined with the given ‘left’ value.
getLeftsFor(right)
Returns the Set of ‘left’ values that are joined with the given ‘right’ value.
getLefts()
Returns a Set of all the ‘left’ values in the table.
getRights()
Returns a Set of all the ‘right’ values in the table.
size
The number of joins currently in the table. Note that joins are unique, so if you call .add(x, y)
twice in a row, the second call will have no effect on the size.
Iterating
Join tables are iterable. Each iteration receives a two-item array in the form [left, right]
:
const table = ; table;table;table; for const animal food of table console;// cow eats grass// rabbit eats carrots// rabbit eats lettuce
Warning: mutating the table while you're iterating over it might have unpredictable results. If you need to update the table during a loop, you might want to spread the table into an array first:
for const x y of ...table // safe to update table here
License
MIT