使用 Javascript 在上传文件之前显示图像和验证图像扩展名

Question

我的目标是首先验证上传文件是一个图像，如果它是一个图像，我将显示它。 我从Validation Code和Image Code获得代码。

起初我能够显示图像。 但是，当我将显示图像代码与验证代码结合使用时，我无法同时进行验证和显示。

谁能帮帮我吗？ 下面是我的代码。 提前致谢！ :)

<input type="file" name="dataFile" id="fileChooser" onchange="readURL(this);" />





<SCRIPT type="text/javascript">

var _validFileExtensions = [".jpg", ".jpeg", ".bmp", ".gif", ".png"];

     function readURL(input) {

         var arrInputs = document.getElementById("fileChooser").value;
            for (var i = 0; i < arrInputs.length; i++) {
                var oInput = arrInputs[i];
                if (oInput.type == "file") {
                    var sFileName = oInput.value;
                if (sFileName.length > 0) {
                    var blnValid = false;
                    for (var j = 0; j < _validFileExtensions.length; j++) {
                        var sCurExtension = _validFileExtensions[j];
                        if (sFileName.substr(sFileName.length - sCurExtension.length, sCurExtension.length).toLowerCase() == sCurExtension.toLowerCase()) {
                            blnValid = true;

                            if (input.files && input.files[0])  {
                                var reader = new FileReader();

                                reader.onload = function (e) {
                                    $('#blah').attr('src', e.target.result)
                                };

                                reader.readAsDataURL(input.files[0]);
                            }


                            break;
                        }
                    }

                    if (!blnValid) {
                        alert("Sorry, " + sFileName + " is invalid, allowed extensions are: " + _validFileExtensions.join(", "));
                        return false;
                    }
                }
            }
        }

        return true;





    }

Answer 1

我能够解决它。 下面是正确的代码。 :)

JavaScript

<SCRIPT type="text/javascript">
    function ValidateFileUpload() {
        var fuData = document.getElementById('fileChooser');
        var FileUploadPath = fuData.value;

//To check if user upload any file
        if (FileUploadPath == '') {
            alert("Please upload an image");

        } else {
            var Extension = FileUploadPath.substring(
                    FileUploadPath.lastIndexOf('.') + 1).toLowerCase();

//The file uploaded is an image

if (Extension == "gif" || Extension == "png" || Extension == "bmp"
                    || Extension == "jpeg" || Extension == "jpg") {

// To Display
                if (fuData.files && fuData.files[0]) {
                    var reader = new FileReader();

                    reader.onload = function(e) {
                        $('#blah').attr('src', e.target.result);
                    }

                    reader.readAsDataURL(fuData.files[0]);
                }

            } 

//The file upload is NOT an image
else {
                alert("Photo only allows file types of GIF, PNG, JPG, JPEG and BMP. ");

            }
        }
    }
</SCRIPT>

更改输入：

<input type="file" name="dataFile" id="fileChooser" onchange="return ValidateFileUpload()" />

要在上传前显示图像：

<img src="images/noimg.jpg" id="blah">

Answer 2

我们解决了它..这是完整的代码:)此代码将帮助您

1. 上传并显示图片（非上传功能）
2. 图像扩展验证
3. 重置img以防验证返回 false

 function show(input) { debugger; var validExtensions = ['jpg','png','jpeg']; //array of valid extensions var fileName = input.files[0].name; var fileNameExt = fileName.substr(fileName.lastIndexOf('.') + 1); if ($.inArray(fileNameExt, validExtensions) == -1) { input.type = '' input.type = 'file' $('#user_img').attr('src',""); alert("Only these file types are accepted : "+validExtensions.join(', ')); } else { if (input.files && input.files[0]) { var filerdr = new FileReader(); filerdr.onload = function (e) { $('#user_img').attr('src', e.target.result); } filerdr.readAsDataURL(input.files[0]); } } }

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> <div class="form-group"> Upload Your Image <div class="col-md-10"> <div> <img id="user_img" height="130" width="130" style="border:solid" /> </div> <div> <input type="file" title="search image" id="file" name="file" onchange="show(this)" /> </div> </div> </div>

Answer 3

function isValidPhoto(fileName)
{
    var allowed_extensions = new Array("jpg","png");
    var file_extension = fileName.split('.').pop().toLowerCase(); 

    for(var i = 0; i <= allowed_extensions.length; i++)
    {
        if(allowed_extensions[i] == file_extension)
        {
            return true; // valid file extension
        }
    }

    return false;
}