jquery 选择本地图片

<input type="file" id="imageUpload" accept="image/*">
<img id="previewImage" src="" alt="Preview">

$(document).ready(function() {
    $('#imageUpload').on('change', function() {
        var file = this.files[0];
        if (file) {
            var reader = new FileReader();
            reader.onload = function(e) {
                $('#previewImage').attr('src', e.target.result);
            };
            reader.readAsDataURL(file);
        }
    });
});

$(document).ready(function() {
    $('#imageUpload').on('change', function() {
        var file = this.files[0];
        if (file && file.type.startsWith('image/')) {
            var reader = new FileReader();
            reader.onload = function(e) {
                $('#previewImage').attr('src', e.target.result);
            };
            reader.readAsDataURL(file);
        } else {
            alert('请选择一个有效的图片文件');
        }
    });
});