<body>
<input type="file" id="aa"/>
<button id="btn">aaa</button>
<img id="img" src="" alt="">
</body>
<script>
document.getElementById("btn").onclick = function () {
var img = document.getElementById("aa").files[0];
var oFReader = new FileReader();
oFReader.readAsDataURL(img);
oFReader.onload = function (oFREvent) { //当读取操作成功完成时调用.
document.getElementById("video").src = oFREvent.target.result;
data = window.URL.createObjectURL(new Blob([oFREvent.target.result]));
};
}
</script>
详情见：https://developer.mozilla.org/zh-CN/docs/Web/API/FileReader