Incr/Decr

Incr

incr can be used to increment the value of a given key in a single command.

// Increment myCountValue by 1, returns a promise
client.incr('myCountValue');

Decr

decr can be used to decrement the value of a given key in a single command.

// Decrement myCountValue by 1, returns a promise
client.decr('myCountValue');

Notes

In cases where you just want to increase or decrease the value of an item, using incr/decr makes a lot more sense than performing a get then increasing or decreasing its value then performing a set.

It is also helpful to eliminate race conditions. For example, if your Memcached server is shared by multiple hosts and multiple want to increment a key, you could have a scenario where both hosts perform the get, then increment then both perform the set. In this case where you'd expect the value to be incremented by 2, it may instead be incremented only by 1 because the two fought and neither won.

Using increment eliminates those kinds of race conditions since the whole thing is performed in a single Memcached command.

Defaults to 1

In the simplest case, if you provide no increment amount, Memcache Plus will increment or decrement the supplied key by 1. It will then resolve the Promise with the updated value of that item.

client
    .incr('myCountValue')
    .then(function(val) {
        // The new value will be exactly 1 more than the old one
        console.log('the new value of myCountValue is', val);
    });

Can specify incr/decr amount

However, you can also specify an increment/decrement amount. For instance, to decrement a number by 5:

client
    .decr('myCountValue', 5)
    .then(function(val) {
        // The new value will be exactly 5 less than the old one
        console.log('the new value of myCountValue is', val);
    });

Only works on numeric types

Since it makes no sense to increment something like "banana" or { "foo": "bar" }, incr and decr can only be used to increment numeric types.