chushihua

node_modules/throttle-debounce/throttle.js

@@ -0,0 +1,91 @@
+/* eslint-disable no-undefined,no-param-reassign,no-shadow */
+
+/**
+ * Throttle execution of a function. Especially useful for rate limiting
+ * execution of handlers on events like resize and scroll.
+ *
+ * @param  {Number}    delay          A zero-or-greater delay in milliseconds. For event callbacks, values around 100 or 250 (or even higher) are most useful.
+ * @param  {Boolean}   [noTrailing]   Optional, defaults to false. If noTrailing is true, callback will only execute every `delay` milliseconds while the
+ *                                    throttled-function is being called. If noTrailing is false or unspecified, callback will be executed one final time
+ *                                    after the last throttled-function call. (After the throttled-function has not been called for `delay` milliseconds,
+ *                                    the internal counter is reset)
+ * @param  {Function}  callback       A function to be executed after delay milliseconds. The `this` context and all arguments are passed through, as-is,
+ *                                    to `callback` when the throttled-function is executed.
+ * @param  {Boolean}   [debounceMode] If `debounceMode` is true (at begin), schedule `clear` to execute after `delay` ms. If `debounceMode` is false (at end),
+ *                                    schedule `callback` to execute after `delay` ms.
+ *
+ * @return {Function}  A new, throttled, function.
+ */
+module.exports = function ( delay, noTrailing, callback, debounceMode ) {
+
+	// After wrapper has stopped being called, this timeout ensures that
+	// `callback` is executed at the proper times in `throttle` and `end`
+	// debounce modes.
+	var timeoutID;
+
+	// Keep track of the last time `callback` was executed.
+	var lastExec = 0;
+
+	// `noTrailing` defaults to falsy.
+	if ( typeof noTrailing !== 'boolean' ) {
+		debounceMode = callback;
+		callback = noTrailing;
+		noTrailing = undefined;
+	}
+
+	// The `wrapper` function encapsulates all of the throttling / debouncing
+	// functionality and when executed will limit the rate at which `callback`
+	// is executed.
+	function wrapper () {
+
+		var self = this;
+		var elapsed = Number(new Date()) - lastExec;
+		var args = arguments;
+
+		// Execute `callback` and update the `lastExec` timestamp.
+		function exec () {
+			lastExec = Number(new Date());
+			callback.apply(self, args);
+		}
+
+		// If `debounceMode` is true (at begin) this is used to clear the flag
+		// to allow future `callback` executions.
+		function clear () {
+			timeoutID = undefined;
+		}
+
+		if ( debounceMode && !timeoutID ) {
+			// Since `wrapper` is being called for the first time and
+			// `debounceMode` is true (at begin), execute `callback`.
+			exec();
+		}
+
+		// Clear any existing timeout.
+		if ( timeoutID ) {
+			clearTimeout(timeoutID);
+		}
+
+		if ( debounceMode === undefined && elapsed > delay ) {
+			// In throttle mode, if `delay` time has been exceeded, execute
+			// `callback`.
+			exec();
+
+		} else if ( noTrailing !== true ) {
+			// In trailing throttle mode, since `delay` time has not been
+			// exceeded, schedule `callback` to execute `delay` ms after most
+			// recent execution.
+			//
+			// If `debounceMode` is true (at begin), schedule `clear` to execute
+			// after `delay` ms.
+			//
+			// If `debounceMode` is false (at end), schedule `callback` to
+			// execute after `delay` ms.
+			timeoutID = setTimeout(debounceMode ? clear : exec, debounceMode === undefined ? delay - elapsed : delay);
+		}
+
+	}
+
+	// Return the wrapper function.
+	return wrapper;
+
+};