错误：无法在“节点”上执行“ appendChild”：在JavaScript中使用微调器时参数1不是“节点”类型

问题描述

我在从引用的javascript代码中实现了微调器，但出现错误-

错误：无法在“节点”上执行“ appendChild”：参数1不是“节点”类型

码：

app.js

    render() {


    var opts = {
        lines: 13, // The number of lines to draw
        length: 38, // The length of each line
        width: 17, // The line thickness
        radius: 45, // The radius of the inner circle
        scale: 1, // Scales overall size of the spinner
        corners: 1, // Corner roundness (0..1)
        color: '#5229cc', // CSS color or array of colors
       //more
      };

       var target = document.getElementById('viz');
    //  var spinner = new Spinner(opts).spin(target);

        var spinner = new Spinner().spin();
        target.appendChild(spinner.el);


          //code
                },
                onCompleted: function () {
                    var target = document.getElementById('viz');
                    var spinner = new Spinner().stop();

                    target.appendChild(spinner.el);


                  session.close();
                 //code

        };