| import isObject from './isObject.js' | |
| /** | |
| * Creates a debounced function that delays invoking `func` until after `wait` | |
| * milliseconds have elapsed since the last time the debounced function was | |
| * invoked. The debounced function comes with a `cancel` method to cancel | |
| * delayed `func` invocations and a `flush` method to immediately invoke them. | |
| * Provide `options` to indicate whether `func` should be invoked on the | |
| * leading and/or trailing edge of the `wait` timeout. The `func` is invoked | |
| * with the last arguments provided to the debounced function. Subsequent | |
| * calls to the debounced function return the result of the last `func` | |
| * invocation. | |
| * | |
| * **Note:** If `leading` and `trailing` options are `true`, `func` is | |
| * invoked on the trailing edge of the timeout only if the debounced function | |
| * is invoked more than once during the `wait` timeout. | |
| * | |
| * If `wait` is `0` and `leading` is `false`, `func` invocation is deferred | |
| * until the next tick, similar to `setTimeout` with a timeout of `0`. | |
| * | |
| * See [David Corbacho's article](https://css-tricks.com/debouncing-throttling-explained-examples/) | |
| * for details over the differences between `debounce` and `throttle`. | |
| * | |
| * @since 0.1.0 | |
| * @category Function | |
| * @param {Function} func The function to debounce. | |
| * @param {number} [wait=0] The number of milliseconds to delay. | |
| * @param {Object} [options={}] The options object. | |
| * @param {boolean} [options.leading=false] | |
| * Specify invoking on the leading edge of the timeout. | |
| * @param {number} [options.maxWait] | |
| * The maximum time `func` is allowed to be delayed before it's invoked. | |
| * @param {boolean} [options.trailing=true] | |
| * Specify invoking on the trailing edge of the timeout. | |
| * @returns {Function} Returns the new debounced function. | |
| * @example | |
| * | |
| * // Avoid costly calculations while the window size is in flux. | |
| * jQuery(window).on('resize', debounce(calculateLayout, 150)) | |
| * | |
| * // Invoke `sendMail` when clicked, debouncing subsequent calls. | |
| * jQuery(element).on('click', debounce(sendMail, 300, { | |
| * 'leading': true, | |
| * 'trailing': false | |
| * })) | |
| * | |
| * // Ensure `batchLog` is invoked once after 1 second of debounced calls. | |
| * const debounced = debounce(batchLog, 250, { 'maxWait': 1000 }) | |
| * const source = new EventSource('/stream') | |
| * jQuery(source).on('message', debounced) | |
| * | |
| * // Cancel the trailing debounced invocation. | |
| * jQuery(window).on('popstate', debounced.cancel) | |
| */ | |
| function debounce(func, wait, options) { | |
| let lastArgs, | |
| lastThis, | |
| maxWait, | |
| result, | |
| timerId, | |
| lastCallTime | |
| let lastInvokeTime = 0 | |
| let leading = false | |
| let maxing = false | |
| let trailing = true | |
| if (typeof func != 'function') { | |
| throw new TypeError('Expected a function') | |
| } | |
| wait = +wait || 0 | |
| if (isObject(options)) { | |
| leading = !!options.leading | |
| maxing = 'maxWait' in options | |
| maxWait = maxing ? Math.max(+options.maxWait || 0, wait) : maxWait | |
| trailing = 'trailing' in options ? !!options.trailing : trailing | |
| } | |
| function invokeFunc(time) { | |
| const args = lastArgs | |
| const thisArg = lastThis | |
| lastArgs = lastThis = undefined | |
| lastInvokeTime = time | |
| result = func.apply(thisArg, args) | |
| return result | |
| } | |
| function leadingEdge(time) { | |
| // Reset any `maxWait` timer. | |
| lastInvokeTime = time | |
| // Start the timer for the trailing edge. | |
| timerId = setTimeout(timerExpired, wait) | |
| // Invoke the leading edge. | |
| return leading ? invokeFunc(time) : result | |
| } | |
| function remainingWait(time) { | |
| const timeSinceLastCall = time - lastCallTime | |
| const timeSinceLastInvoke = time - lastInvokeTime | |
| const result = wait - timeSinceLastCall | |
| return maxing ? Math.min(result, maxWait - timeSinceLastInvoke) : result | |
| } | |
| function shouldInvoke(time) { | |
| const timeSinceLastCall = time - lastCallTime | |
| const timeSinceLastInvoke = time - lastInvokeTime | |
| // Either this is the first call, activity has stopped and we're at the | |
| // trailing edge, the system time has gone backwards and we're treating | |
| // it as the trailing edge, or we've hit the `maxWait` limit. | |
| return (lastCallTime === undefined || (timeSinceLastCall >= wait) || | |
| (timeSinceLastCall < 0) || (maxing && timeSinceLastInvoke >= maxWait)) | |
| } | |
| function timerExpired() { | |
| const time = Date.now() | |
| if (shouldInvoke(time)) { | |
| return trailingEdge(time) | |
| } | |
| // Restart the timer. | |
| timerId = setTimeout(timerExpired, remainingWait(time)) | |
| } | |
| function trailingEdge(time) { | |
| timerId = undefined | |
| // Only invoke if we have `lastArgs` which means `func` has been | |
| // debounced at least once. | |
| if (trailing && lastArgs) { | |
| return invokeFunc(time) | |
| } | |
| lastArgs = lastThis = undefined | |
| return result | |
| } | |
| function cancel() { | |
| if (timerId !== undefined) { | |
| clearTimeout(timerId) | |
| } | |
| lastInvokeTime = 0 | |
| lastArgs = lastCallTime = lastThis = timerId = undefined | |
| } | |
| function flush() { | |
| return timerId === undefined ? result : trailingEdge(Date.now()) | |
| } | |
| function debounced(...args) { | |
| const time = Date.now() | |
| const isInvoking = shouldInvoke(time) | |
| lastArgs = args | |
| lastThis = this | |
| lastCallTime = time | |
| if (isInvoking) { | |
| if (timerId === undefined) { | |
| return leadingEdge(lastCallTime) | |
| } | |
| if (maxing) { | |
| // Handle invocations in a tight loop. | |
| timerId = setTimeout(timerExpired, wait) | |
| return invokeFunc(lastCallTime) | |
| } | |
| } | |
| if (timerId === undefined) { | |
| timerId = setTimeout(timerExpired, wait) | |
| } | |
| return result | |
| } | |
| debounced.cancel = cancel | |
| debounced.flush = flush | |
| return debounced | |
| } | |
| export default debounce |
