Add an options object argument to _.debounce and _.throttle. [closes #222]

Former-commit-id: d5eb3bc21d4a5c6d25314153f98d43a3d11eb4fa

build/pre-compile.js

@@ -156,6 +156,7 @@
     'keys',
     'last',
     'lastIndexOf',
+    'leading',
     'map',
     'max',
     'memoize',
@@ -204,6 +205,7 @@
     'throttle',
     'times',
     'toArray',
+    'trailing',
     'unescape',
     'unindexedChars',
     'union',

lodash.js

@@ -4440,44 +4440,53 @@
     /**
      * Creates a function that will delay the execution of `func` until after
      * `wait` milliseconds have elapsed since the last time it was invoked. Pass
-     * `true` for `immediate` to cause debounce to invoke `func` on the leading,
-     * instead of the trailing, edge of the `wait` timeout. Subsequent calls to
-     * the debounced function will return the result of the last `func` call.
+     * an `options` object to indicate that `func` should be invoked on the leading
+     * and/or trailing edge of the `wait` timeout. Subsequent calls to the debounced
+     * function will return the result of the last `func` call.
      *
      * @static
      * @memberOf _
      * @category Functions
      * @param {Function} func The function to debounce.
      * @param {Number} wait The number of milliseconds to delay.
-     * @param {Boolean} immediate A flag to indicate execution is on the leading
-     *  edge of the timeout.
+     * @param {Object} options The options object.
+     *  [leading=false] A boolean to specify execution on the leading edge of the timeout.
+     *  [trailing=true] A boolean to specify execution on the trailing edge of the timeout.
      * @returns {Function} Returns the new debounced function.
      * @example
      *
      * var lazyLayout = _.debounce(calculateLayout, 300);
      * jQuery(window).on('resize', lazyLayout);
      */
-    function debounce(func, wait, immediate) {
+    function debounce(func, wait, options) {
       var args,
           result,
           thisArg,
-          timeoutId;
+          timeoutId,
+          trailing = true;
 
       function delayed() {
         timeoutId = null;
-        if (!immediate) {
+        if (trailing) {
           result = func.apply(thisArg, args);
         }
       }
+      if (options === true) {
+        var leading = true;
+        trailing = false;
+      } else if (options) {
+        leading = options.leading;
+        trailing = options.trailing;
+      }
       return function() {
-        var isImmediate = immediate && !timeoutId;
+        var isLeading = leading && !timeoutId;
         args = arguments;
         thisArg = this;
 
         clearTimeout(timeoutId);
         timeoutId = setTimeout(delayed, wait);
 
-        if (isImmediate) {
+        if (isLeading) {
           result = func.apply(thisArg, args);
         }
         return result;
@@ -4647,39 +4656,57 @@
     }
 
     /**
-     * Creates a function that, when executed, will only call the `func`
-     * function at most once per every `wait` milliseconds. If the throttled
-     * function is invoked more than once during the `wait` timeout, `func` will
-     * also be called on the trailing edge of the timeout. Subsequent calls to the
-     * throttled function will return the result of the last `func` call.
+     * Creates a function that, when executed, will only call the `func` function
+     * at most once per every `wait` milliseconds. If the throttled function is
+     * invoked more than once during the `wait` timeout, `func` will also be called
+     * on the trailing edge of the timeout. Pass an `options` object to indicate
+     * that `func` should be invoked on the leading and/or trailing edge of the
+     * `wait` timeout. Subsequent calls to the throttled function will return
+     * the result of the last `func` call.
      *
      * @static
      * @memberOf _
      * @category Functions
      * @param {Function} func The function to throttle.
      * @param {Number} wait The number of milliseconds to throttle executions to.
+     * @param {Object} options The options object.
+     *  [leading=true] A boolean to specify execution on the leading edge of the timeout.
+     *  [trailing=true] A boolean to specify execution on the trailing edge of the timeout.
      * @returns {Function} Returns the new throttled function.
      * @example
      *
      * var throttled = _.throttle(updatePosition, 100);
      * jQuery(window).on('scroll', throttled);
      */
-    function throttle(func, wait) {
+    function throttle(func, wait, options) {
       var args,
           result,
           thisArg,
           timeoutId,
-          lastCalled = 0;
+          lastCalled = 0,
+          leading = true,
+          trailing = true;
 
       function trailingCall() {
         lastCalled = new Date;
         timeoutId = null;
-        result = func.apply(thisArg, args);
+
+        if (trailing) {
+          result = func.apply(thisArg, args);
+        }
+      }
+      if (options === false) {
+        leading = false;
+      } else if (options) {
+        leading = options.leading;
+        trailing = options.trailing;
       }
       return function() {
-        var now = new Date,
-            remaining = wait - (now - lastCalled);
-
+        var now = new Date;
+        if (!timeoutId && !leading) {
+          lastCalled = now;
+        }
+        var remaining = wait - (now - lastCalled);
         args = arguments;
         thisArg = this;