基础 - 验证文件类型

<input id="show" type="file" />

window.onload = function () {

    var oShow = document.getElementById("show");
    oShow.onchange = function () {

        var filePath = this.value;
        var suxPath = filePath.substr(filePath.lastIndexOf(".")+1).toUpperCase();
        console.log(suxPath);
    }

}