您需要在包含helpers.js文件之前声明变量。只需在helpers.js的include上方创建一个脚本标签,然后在其中定义它。
<script type='text/javascript' >
var myFunctionTag = false;
</script>
<script type='text/javascript' src='js/helpers.js'></script>
...
<script type='text/javascript' >
// rest of your code, which may depend on helpers.js
</script>