Function debounce

ui/media/js/utils.js:390–430

A debounce is a higher-order function, which is a function that returns another function * that, as long as it continues to be invoked, will not be triggered. * The function will be called after it stops being called for N milliseconds. * If `immediate` is passed, trigger the function on the lead

(func, wait, immediate)

 * @Returns a promise that will resolve to func return value.
 */
function debounce(func, wait, immediate) {
    if (typeof wait === "undefined") {
        wait = 40
    }
    if (typeof wait !== "number") {
        throw new Error("wait is not an number.")
    }
    let timeout = null
    let lastPromiseSrc = new PromiseSource()
    const applyFn = function (context, args) {
        let result = undefined
        try {
            result = func.apply(context, args)
        } catch (err) {
            lastPromiseSrc.reject(err)
        }
        if (result instanceof Promise) {
            result.then(lastPromiseSrc.resolve, lastPromiseSrc.reject)
        } else {
            lastPromiseSrc.resolve(result)
        }
    }
    return function (...args) {
        const callNow = Boolean(immediate && !timeout)
        const context = this
        if (timeout) {
            clearTimeout(timeout)
        }
        timeout = setTimeout(function () {
            if (!immediate) {
                applyFn(context, args)
            }
            lastPromiseSrc = new PromiseSource()
            timeout = null
        }, wait)
        if (callNow) {
            applyFn(context, args)
        }
        return lastPromiseSrc.promise
    }
}

function preventNonNumericalInput(e) {
    e = e || window.event