JavaScript 防抖

debounce.js

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;
    }