将函数的引用作为回调传递返回undefined

Question

我有以下代码：

var BE = BE || {};

BE.UiEvents = function(s) {
    this.collapseForm = $(s.collapseForm);
    this.showmenu = $(s.showmenu);
    this.searchTrigger = $(s.searchTrigger);
    this.arrowDownIcon = s.arrowDownIcon;
    this.arrowUpIcon = s.arrowUpIcon;
    this.datePicker = $(s.datePicker);

    return this;
};

BE.UiEvents.prototype.show_menu = function(e) {
    console.log(this.collapseForm);
};

在“document.ready”里面我这样做：

var t = new BE.UiEvents({
    collapseForm: '.collapse-form',
    showmenu: '#showmenu>span',
    searchTrigger: '.default-orange.search-again',
    arrowDownIcon: 'fa-chevron-down',
    arrowUpIcon: 'fa-chevron-up',
    datePicker: 'input[name=dateStartDatePickerWidget]'
});

t.show_menu();

$('#showmenu').off('click').on('click', t.show_menu);

当我调用“t.show_menu”时，它会输出console.log语句。 但是“点击”它会返回undefined。