uncaught typeError:无法读取属性'querySelectorAll'的null

Question

我想在网站上使用此菜单移动设备. http://tympanus.net/codrops/2013/08/13/multi-level-push-menu/comment-page-8/#comment-466199

我有它工作,但一个ie11用户报告错误,我在控制台Uncaught TypeError中看到以下错误:无法读取属性'querySelectorAll'的nullmlPushMenu._init @ mlpushmenu.js:89mlPushMenu @ mlpushmenu.js:67(匿名函数) @(指数):1062

这是有问题的js文件的片段

function mlPushMenu( el, trigger, options ) {   
    this.el = el;
    this.trigger = trigger;
    this.options = extend( this.defaults, options );
    // support 3d transforms
    this.support = Modernizr.csstransforms3d;
    if( this.support ) {
        this._init();
    }
}

mlPushMenu.prototype = {
    defaults : {
        // overlap: there will be a gap between open levels
        // cover: the open levels will be on top of any previous open level
        type : 'overlap', // overlap || cover
        // space between each overlaped level
        levelSpacing : 40,
        // classname for the element (if any) that when clicked closes the current level
        backClass : 'mp-back'
    },
    _init : function() {
        // if menu is open or not
        this.open = false;
        // level depth
        this.level = 0;
        // the moving wrapper
        this.wrapper = document.getElementById( 'mp-pusher' );
        // the mp-level elements
        this.levels = Array.prototype.slice.call( this.el.querySelectorAll( 'div.mp-level' ) );
        // save the depth of each of these mp-level elements
        var self = this;
        this.levels.forEach( function( el, i ) { el.setAttribute( 'data-level', getLevelDepth( el, self.el.id, 'mp-level' ) ); } );
        // the menu items
        this.menuItems = Array.prototype.slice.call( this.el.querySelectorAll( 'li' ) );
        // if type == "cover" these will serve as hooks to move back to the previous level
        this.levelBack = Array.prototype.slice.call( this.el.querySelectorAll( '.' + this.options.backClass ) );
        // event type (if mobile use touch events)
        this.eventtype = mobilecheck() ? 'touchstart' : 'click';
        // add the class mp-overlap or mp-cover to the main element depending on options.type
        classie.add( this.el, 'mp-' + this.options.type );
        // initialize / bind the necessary events
        this._initEvents();
    },

特定的线89位于其中间,所以这里它被拉出来为您的方向

this.levels = Array.prototype.slice.call( this.el.querySelectorAll( 'div.mp-level' ) );

然后我在我的页脚中调用了插件的实例(即索引行1082

那个电话看起来像这样

<script>
    new mlPushMenu(
        document.getElementById( 'mp-menu' ),
        document.getElementById( 'trigger' ),
        { type : 'cover' }
    );
</script>

Answer 1

您的桌面网站没有ID为" mp-menu " 的元素.当你调用getElementById方法时,你就会得到null回应.然后将其分配给el对象的属性.当您尝试调用querySelectorAll时,您尝试从null值执行此操作.

根据上述问题的评论,mp-menu元素仅存在于移动网站上.如果是这种情况,此代码也应仅在移动设备上加载.