add hw2

node_modules/lodash-es/throttle.js

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+import debounce from './debounce.js';
+import isObject from './isObject.js';
+
+/** Error message constants. */
+var FUNC_ERROR_TEXT = 'Expected a function';
+
+/**
+ * Creates a throttled function that only invokes `func` at most once per
+ * every `wait` milliseconds. The throttled 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
+ * throttled function. Subsequent calls to the throttled 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 throttled 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 `_.throttle` and `_.debounce`.
+ *
+ * @static
+ * @memberOf _
+ * @since 0.1.0
+ * @category Function
+ * @param {Function} func The function to throttle.
+ * @param {number} [wait=0] The number of milliseconds to throttle invocations to.
+ * @param {Object} [options={}] The options object.
+ * @param {boolean} [options.leading=true]
+ *  Specify invoking on the leading edge of the timeout.
+ * @param {boolean} [options.trailing=true]
+ *  Specify invoking on the trailing edge of the timeout.
+ * @returns {Function} Returns the new throttled function.
+ * @example
+ *
+ * // Avoid excessively updating the position while scrolling.
+ * jQuery(window).on('scroll', _.throttle(updatePosition, 100));
+ *
+ * // Invoke `renewToken` when the click event is fired, but not more than once every 5 minutes.
+ * var throttled = _.throttle(renewToken, 300000, { 'trailing': false });
+ * jQuery(element).on('click', throttled);
+ *
+ * // Cancel the trailing throttled invocation.
+ * jQuery(window).on('popstate', throttled.cancel);
+ */
+function throttle(func, wait, options) {
+  var leading = true,
+      trailing = true;
+
+  if (typeof func != 'function') {
+    throw new TypeError(FUNC_ERROR_TEXT);
+  }
+  if (isObject(options)) {
+    leading = 'leading' in options ? !!options.leading : leading;
+    trailing = 'trailing' in options ? !!options.trailing : trailing;
+  }
+  return debounce(func, wait, {
+    'leading': leading,
+    'maxWait': wait,
+    'trailing': trailing
+  });
+}
+
+export default throttle;