html:
<input type="file" onchange="onChange(event,this)">
<img src="" id="preview" height="200" alt="Image preview...">
js：
function onChange(event) {
var file = event.target.files[0];
var reader = new FileReader();
reader.readAsText(file);
reader.onload = function(event) {
preview.src = event.target.result;
};
}
