js input的常用事件

1.text输入框的value值不是数字替换为空

html代码

<input type="text" style="width:150px" id="ts_math_input" placeholder="请输入题：" />

js代码

    ts_math_input.oninput = function () {
        console.log(9);
        event.target.value=event.target.value.replace(/[^0-9]/g,'')
    }

2.file单文件，部分类型文件简单读写

html代码

<input type="file" onchange="change(event)">
<img src="" id="image" alt="">

js代码

   function change(e) {
        let readerfile = e.currentTarget.files[0];
        console.log(readerfile);
        const reader = new FileReader();
        //对于json类型文件，有需要转成json.parse格式的文件
        if (readerfile.type == "application/json") {
            reader.onload = function () {
                var result = JSON.parse(reader.result)
                console.log(result);
            }
            reader.readAsText(readerfile);
        }else if(readerfile.type == "image/png"){
            //png图片
            reader.onload = function () {
                image.src = reader.result;
            }
            reader.readAsDataURL(readerfile);
        } else {
            reader.onload = function () {
                console.log(reader.result);
            }
            reader.readAsText(readerfile);
        }

    }

2.file单文件判断文件大小

html代码

<input type="file" onchange="fileSize(event)">

js代码

function fileSize(){
     let readerfile = e.currentTarget.files[0];
        console.log(readerfile);
        if (readerfile.size == 0) {
            return '0B'
        } else if (!readerfile.size) {
            return '-'
        }
        let fileSizeByte = readerfile.size;
        let fileSizeMsg = "";
        if (fileSizeByte > 0 && fileSizeByte < 1024) {
            fileSizeMsg = fileSizeByte + 'B';
        } else if (fileSizeByte == 1024) {
            fileSizeMsg = "1KB";
        } else if (fileSizeByte > 1024 && fileSizeByte < 1048576) {
            fileSizeMsg = (fileSizeByte / 1024).toFixed(2) + "KB";
        } else if (fileSizeByte == 1048576) {
            fileSizeMsg = "1MB";
        } else if (fileSizeByte > 1048576 && fileSizeByte < 1073741824) {
            fileSizeMsg = (fileSizeByte / (1024 * 1024)).toFixed(2) + "MB";
        } else if (fileSizeByte > 1048576 && fileSizeByte == 1073741824) {
            fileSizeMsg = "1GB";
        } else if (fileSizeByte > 1073741824 && fileSizeByte < 1099511627776) {
            fileSizeMsg = (fileSizeByte / (1024 * 1024 * 1024)).toFixed(2) + "GB";
        } else {
            fileSizeMsg = "文件超过1TB";
        }
        console.log(fileSizeMsg);
}