Question

写JS的时候遇到的问题。Uncaught TypeError: Cannot read property 'style' of null

window.onload=function(){ window.onscroll = function(){ var t = document.documentElement.scrollTop || document.body.scrollTop; var posi_box = document.getElementById( "posi_box" ); if( t >= 900 ) { posi_box.style.position = 'fixed'; } else { posi_box.style.position = 'static'; } }}Uncaught TypeError: Cannot read property 'style' of null at window.onscroll我没看出来我写错了,求指导

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Answer 1

跟踪一下你获取的元素是否存在，最好加一个判断,

var posi_box = document.getElementById( "posi_box" );

if(posi_box)

{

}

以下是还原的示例：