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var isObject = require('../lang/isObject'),
now = require('../date/now');
/** Used as the `TypeError` message for "Functions" methods. */
var FUNC_ERROR_TEXT = 'Expected a function';
/* Native method references for those with the same name as other `lodash` methods. */
var nativeMax = Math.max;
/**
* Creates a function that delays invoking `func` until after `wait` milliseconds
* have elapsed since the last time it was invoked. The created function comes
* with a `cancel` method to cancel delayed invocations. Provide 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 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 the debounced function is
* invoked more than once during the `wait` timeout.
*
* See [David Corbacho's article](http://drupalmotion.com/article/debounce-and-throttle-visual-explanation)
* for details over the differences between `_.debounce` and `_.throttle`.
*
* @static
* @memberOf _
* @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 is 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 the click event is fired, debouncing subsequent calls
* jQuery('#postbox').on('click', _.debounce(sendMail, 300, {
* 'leading': true,
* 'trailing': false
* }));
*
* // ensure `batchLog` is invoked once after 1 second of debounced calls
* var source = new EventSource('/stream');
* jQuery(source).on('message', _.debounce(batchLog, 250, {
* 'maxWait': 1000
* }));
*
* // cancel a debounced call
* var todoChanges = _.debounce(batchLog, 1000);
* Object.observe(models.todo, todoChanges);
*
* Object.observe(models, function(changes) {
* if (_.find(changes, { 'user': 'todo', 'type': 'delete'})) {
* todoChanges.cancel();
* }
* }, ['delete']);
*
* // ...at some point `models.todo` is changed
* models.todo.completed = true;
*
* // ...before 1 second has passed `models.todo` is deleted
* // which cancels the debounced `todoChanges` call
* delete models.todo;
*/
function debounce(func, wait, options) {
var args,
maxTimeoutId,
result,
stamp,
thisArg,
timeoutId,
trailingCall,
lastCalled = 0,
maxWait = false,
trailing = true;
if (typeof func != 'function') {
throw new TypeError(FUNC_ERROR_TEXT);
}
wait = wait < 0 ? 0 : (+wait || 0);
if (options === true) {
var leading = true;
trailing = false;
} else if (isObject(options)) {
leading = options.leading;
maxWait = 'maxWait' in options && nativeMax(+options.maxWait || 0, wait);
trailing = 'trailing' in options ? options.trailing : trailing;
}
function cancel() {
if (timeoutId) {
clearTimeout(timeoutId);
}
if (maxTimeoutId) {
clearTimeout(maxTimeoutId);
}
maxTimeoutId = timeoutId = trailingCall = undefined;
}
function delayed() {
var remaining = wait - (now() - stamp);
if (remaining <= 0 || remaining > wait) {
if (maxTimeoutId) {
clearTimeout(maxTimeoutId);
}
var isCalled = trailingCall;
maxTimeoutId = timeoutId = trailingCall = undefined;
if (isCalled) {
lastCalled = now();
result = func.apply(thisArg, args);
if (!timeoutId && !maxTimeoutId) {
args = thisArg = null;
}
}
} else {
timeoutId = setTimeout(delayed, remaining);
}
}
function maxDelayed() {
if (timeoutId) {
clearTimeout(timeoutId);
}
maxTimeoutId = timeoutId = trailingCall = undefined;
if (trailing || (maxWait !== wait)) {
lastCalled = now();
result = func.apply(thisArg, args);
if (!timeoutId && !maxTimeoutId) {
args = thisArg = null;
}
}
}
function debounced() {
args = arguments;
stamp = now();
thisArg = this;
trailingCall = trailing && (timeoutId || !leading);
if (maxWait === false) {
var leadingCall = leading && !timeoutId;
} else {
if (!maxTimeoutId && !leading) {
lastCalled = stamp;
}
var remaining = maxWait - (stamp - lastCalled),
isCalled = remaining <= 0 || remaining > maxWait;
if (isCalled) {
if (maxTimeoutId) {
maxTimeoutId = clearTimeout(maxTimeoutId);
}
lastCalled = stamp;
result = func.apply(thisArg, args);
}
else if (!maxTimeoutId) {
maxTimeoutId = setTimeout(maxDelayed, remaining);
}
}
if (isCalled && timeoutId) {
timeoutId = clearTimeout(timeoutId);
}
else if (!timeoutId && wait !== maxWait) {
timeoutId = setTimeout(delayed, wait);
}
if (leadingCall) {
isCalled = true;
result = func.apply(thisArg, args);
}
if (isCalled && !timeoutId && !maxTimeoutId) {
args = thisArg = null;
}
return result;
}
debounced.cancel = cancel;
return debounced;
}
module.exports = debounce;
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