当用户选择文件时检查图像文件大小的代码是什么

Question

当用户选择文件时，要添加到以下代码中的代码是什么，以检查图像文件大小，并在文件大小大于5MB时发出警报？它应该首先检查文件扩展名，如果文件扩展名良好，则应检查大小。

<script type="text/javascript">
/*<![CDATA[*/
$("#ProductImage").change(function() {
var f = this.value;
var e = f.replace(/^.*\/, "");
var d = e.split(".").pop();
if (d == "jpg" || d == "jpeg" || d == "png" || d == "gif" || d == "JPG" || d == "JPEG" || d == "PNG" || d == "GIF") {
$("#file_name").val(e)
} else {
alert("Please upload a valid image file.")
}
});
</script>

Answer 1

f.size 将获取文件的大小(以字节为单位(， 5242880 以字节为单位为 5MB

if (f.size >= 5242880){ alert("Image file is too big)}

有关文件大小的详细信息> https://www.w3schools.com/jsref/prop_fileupload_files.asp

Answer 2

嗨，请检查下面的代码

function validateFileExtension(component,msg_id,msg,extns)
{
var flag=0;
with(component)
{
var ext=value.substring(value.lastIndexOf('.')+1);
for(i=0;i<extns.length;i++)
{
if(ext==extns[i])
{
flag=0;
break;
}
else
{
flag=1;
}
}
if(flag!=0)
{
document.getElementById(msg_id).innerHTML=msg;
component.value="";
component.style.backgroundColor="#eab1b1";
component.style.border="thin solid #000000";
component.focus();
return false;
}
else
{
return true;
}
}
}
function validateFileSize(component,maxSize,msg_id,msg)
{
if(navigator.appName=="Microsoft Internet Explorer")
{
if(component.value)
{
var oas=new ActiveXObject("Scripting.FileSystemObject");
var e=oas.getFile(component.value);
var size=e.size;
}
}
else
{
if(component.files[0]!=undefined)
{
size = component.files[0].size;
}
}
if(size!=undefined && size>maxSize)
{
document.getElementById(msg_id).innerHTML=msg;
component.value="";
component.style.backgroundColor="#eab1b1";
component.style.border="thin solid #000000";
component.focus();
return false;
}
else
{
return true;
}
}

另请查看以下代码

function checkFile(e) {
/// get list of files
var file_list = e.target.files;
/// go through the list of files
for (var i = 0, file; file = file_list[i]; i++) {
var sFileName = file.name;
var sFileExtension = sFileName.split('.')[sFileName.split('.').length - 1].toLowerCase();
var iFileSize = file.size;
var iConvert = (file.size / 1048576).toFixed(2);
/// OR together the accepted extensions and NOT it. Then OR the size cond.
/// It's easier to see this way, but just a suggestion - no requirement.
if (!(sFileExtension === "pdf" ||
sFileExtension === "doc" ||
sFileExtension === "docx") || iFileSize > 10485760) { /// 10 mb
txt = "File type : " + sFileExtension + "nn";
txt += "Size: " + iConvert + " MB nn";
txt += "Please make sure your file is in pdf or doc format and less than 10 MB.nn";
alert(txt);
}
}
}