level-modify

Modify an existing key in a levelup store. Uses level-lock to prevent race conditions. See also: level-create, level-move

let db = require('level')('colors.db')
let modify = require('level-modify');
 
function redToBlue(color) {
    if (color === 'red') color = 'blue';
    return color;
}
 
db.put('fence', 'red', (err) => {
    modify(db, 'fence', redToBlue, (err) => {
        if (err && err.code === 'LOCKED') return console.error('conflict');
        db.get('fence', (err, color) => {
            console.log(color); // blue
        });
    });
});

Methods

let modify = require('level-modify');

modify(db, key, mod, callback));

Modify the value at key. mod can be a function in the form of function(oldValue) {return newValue;} or an object which will be merged with the old value like so: Object.assign(oldValue, mod);

If the key is write-locked by a concurrent operation an error will be given to the callback with err.code being 'LOCKED'. Like other levelup methods if callback is omitted errors will be thrown.

Alternatively install onto the db object:

require('level-modify').install(db);

db.modify(key, mod, callback);

License

MIT