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原生JS如何判断 input type='file' 为空,也就是判断用户是否选择了文件
业精于勤，荒于嬉;行成于思，毁于随。
var oInput = document.getElementById('fileInput'); oInput.onchange = function() { if(this.value == '') { alert('empty'); }else { alert(this.value); } }
document.querySelector("input[type=file]").value这样？
document.querySelector("input[type=file]").value
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
document.querySelector("input[type=file]").value这样？