--- /dev/null
+var isObject = require('./isObject'),
+ now = require('./now'),
+ toNumber = require('./toNumber');
+
+/** Error message constants. */
+var FUNC_ERROR_TEXT = 'Expected a function';
+
+/* Built-in method references for those with the same name as other `lodash` methods. */
+var nativeMax = Math.max,
+ nativeMin = Math.min;
+
+/**
+ * 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 to 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`.
+ *
+ * @static
+ * @memberOf _
+ * @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.
+ * var debounced = _.debounce(batchLog, 250, { 'maxWait': 1000 });
+ * var 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) {
+ var lastArgs,
+ lastThis,
+ maxWait,
+ result,
+ timerId,
+ lastCallTime,
+ lastInvokeTime = 0,
+ leading = false,
+ maxing = false,
+ trailing = true;
+
+ if (typeof func != 'function') {
+ throw new TypeError(FUNC_ERROR_TEXT);
+ }
+ wait = toNumber(wait) || 0;
+ if (isObject(options)) {
+ leading = !!options.leading;
+ maxing = 'maxWait' in options;
+ maxWait = maxing ? nativeMax(toNumber(options.maxWait) || 0, wait) : maxWait;
+ trailing = 'trailing' in options ? !!options.trailing : trailing;
+ }
+
+ function invokeFunc(time) {
+ var args = lastArgs,
+ 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) {
+ var timeSinceLastCall = time - lastCallTime,
+ timeSinceLastInvoke = time - lastInvokeTime,
+ result = wait - timeSinceLastCall;
+
+ return maxing ? nativeMin(result, maxWait - timeSinceLastInvoke) : result;
+ }
+
+ function shouldInvoke(time) {
+ var timeSinceLastCall = time - lastCallTime,
+ 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() {
+ var time = 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(now());
+ }
+
+ function debounced() {
+ var time = now(),
+ isInvoking = shouldInvoke(time);
+
+ lastArgs = arguments;
+ 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;
+}
+
+module.exports = debounce;
projects / yaffs-website / blobdiff