为什么我会收到“未捕获的类型错误：无法读取未定义的属性 'body'”？

Question

My JS file is simply

jQuery(function ( $ ) {
    // make elements with class 'same-height-as-width' have the self-explanatory property
    $(window).resize(function ( ) {
        $('.same-height-as-width').each( function ( ) {
            var thisElement = $(this);
            thisElement.height(thisElement.width());        
        });
    });

    window.onscroll = function () {

        var body = document.body; //IE 'quirks'
        var document = document.documentElement; //IE with doctype
        document = (document.clientHeight) ? document : body;

        if (document.scrollTop == 0) {
            alert("top");
        }
    };

});

and the line that is causing me trouble is var body = document.body; //IE 'quirks' var body = document.body; //IE 'quirks' . The error

Uncaught TypeError: Cannot read property 'body' of undefined

is printed to the console every time I scroll. And yet, when I type document.body into the console, the element shows up in the console, is not undefined . I've also tried moving the window.onscroll outside the j Query(function ( $ ) but I get the same error.

Answer 1

这是因为JavaScript 变量提升，但不要让您感到困惑，不要使用“文档”作为变量的名称