overscroll/es/handlers.js

scroll

import pick from 'object.pick';
import compose from './utils/compose';

var noop = function noop() {};

export function handler(name) {
  return function (scope) {
    var mode = scope.mode;

    var wrap = function wrap(func) {
      return function () {
        func.call(scope.target, pick(scope.overscroll, ['scrollTop', 'scrollLeft', 'scrollHeight', 'scrollWidth', 'clientHeight', 'clientWidth'].concat(mode === 'scroll' ? [] : ['section', 'positions'])));
      };
    };
    scope.handleCache = scope.handleCache || {};
    scope.handleCache[name] = noop;
    var initialHandler = scope[name] ? scope[name] : noop;
    scope[name] = function () {
      scope.handleCache[name]();
      wrap(initialHandler)();
    };
    return compose(function (callback) {
      scope.handleCache[name] = scope.handleCache[name] !== noop ? compose(callback, scope.handleCache[name]) : callback;
    }, wrap);
  };
}

export var handleDestroy = handler('onDestroy');
export var handleBeforeScroll = handler('onBeforeScroll');
export var handleAfterScroll = handler('onAfterScroll');
export var handleScroll = handler('onScroll');
export var handleInit = handler('onInit');