Javascript 未捕获的TypeError:无法读取null的属性“getBBox”_Javascript_D3.js

Javascript 未捕获的TypeError:无法读取null的属性“getBBox”

javascript d3.js

Javascript 未捕获的TypeError:无法读取null的属性“getBBox”,javascript,d3.js,Javascript,D3.js,我正在尝试复制，但出现了错误： tank.js:441 Uncaught TypeError: Cannot read property 'getBBox' of null at AnalogTank.calculateArrowPosition (tank.js:441) at AnalogTank.applyArrowAttribute (tank.js:408) at AnalogTank.addArrow (tank.js:404) at AnalogT

我正在尝试复制，但出现了错误：

 tank.js:441 Uncaught TypeError: Cannot read property 'getBBox' of null
    at AnalogTank.calculateArrowPosition (tank.js:441)
    at AnalogTank.applyArrowAttribute (tank.js:408)
    at AnalogTank.addArrow (tank.js:404)
    at AnalogTank.initTower (tank.js:316)
    at AnalogTank.init (tank.js:126)
    at new AnalogTank (tank.js:113)
    at jQuery.fn.init.$.fn.analogTank (tank.js:105)
    at tank.js:1124

它似乎是src中d3的版本=https://cdnjs.cloudflare.com/ajax/libs/d3/4.2.3/d3.js>可能是问题的一部分，但我不知道如何纠正错误

这是我的HTML头供参考

<!DOCTYPE HTML>


<html>
    <head>
        <meta charset="utf-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no" />
        <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.2.3/d3.js"></script>
        <script src="https://code.jquery.com/jquery-3.1.0.js"></script>
        <script src="https://cdnjs.cloudflare.com/ajax/libs/jqueryui/1.12.1/jquery-ui.js"></script>
        <script type="text/javascript" src="tank.js"></script>

        <link rel="stylesheet" href="tank.css" />


    </head>

在加载HTML之前，我不应该尝试加载我的tank.js。我只是将tank.js的标签移到了文档的底部。

tank.js第1124行怎么说？@BenRondeau}jQuery；让tank=$'.wrapper'.analogTank{就像在代码笔中一样。