自定义文件上传按钮的实现方法

1. 
2. 上传

var inputBox = document.getElementById("file-input");

function selectFile(){
    inputBox.click();
}

function upload(){
    var file = inputBox.files[0];
    if (!file) {
        alert('请选择文件');
        return;
    }
    var form = new FormData();
    form.append('file', file);
    var xhr = new XMLHttpRequest();
    xhr.open('post', '../../api/receiveOptionQuestion', true);
    xhr.Onload= function () {
        alert(xhr.responseText);
    };
    xhr.upload.addEventListener('progress', function(e){
        console.log(e.loaded / e.total * 100 + '%');
    }, false);
    xhr.send(form);
}