cancel-via-race.js

function delay(n) { return new Promise(r => setTimeout(r, n)) }

function debounced(ms, action) {
    let cancelPrevious;
    let cancellation = () => new Promise((resolve, reject) => cancelPrevious = reject)
    
    return function (...args) {
        if (cancelPrevious != null) cancelPrevious()
        return Promise.race([cancellation(), delay(ms)])
            .then(() => action.apply(this, args))
    }
}