js在函数体中定义了c_href为全局变量为什么仍旧报错ReferenceError: c_href is not defined？

图片说明

图中文件chapters_href.txt内容为：

/comic/23885/1408578.html--#--/comic/23885/1395147.html--#--/comic/23885/1387036.html--#--/comic/23885/1360258.html--#--

html，JavaScript代码如下：

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>乌拉乌拉</title>
  </head>
  <body>
    <label>选择章节地址文件：</label>
      <input type="file" id="chapters_hreff" />
      <input type="button" id="b4" value="读取全部文件" />

    <script>
    function readAsText(tem,id){//文本读取
    var t=tem;
    console.log(t);
    file = document.getElementById(id).files[0];  
    reader = new FileReader();//将文件以文本形式读入页面
    reader.readAsText(file);  
    reader.onload=function(f){
    jsArr = JSON.stringify(this.result);//对象转字符串
    tem =jsArr.replace(/"/g,'');//删‘”’
    tem = tem.split("--#--");//分割并且字符串转为数组

    if(t=='chapters_href') {
        c_href = tem;
        console.log(c_href);
    }
   }
}


    var wait=false;
        document.getElementById('b4').addEventListener("click",function(){//监听按下id为b4按钮后再执行内容
            var wait=true;
    if(wait){
        readAsText('chapters_href','chapters_hreff');
        console.log(c_href);
    }
    })
    </script>
  </body>
</html>

if(t=='chapters_href') {
c_href = tem;
console.log(c_href);//这里能打印出来吗？条件进去的情况下报错的吗
}

    附上代码：这样写

<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8" />
    <title>the final project</title>
    <link rel="stylesheet" href="css/finalproject.css" />
    <script src="js/finalproject.js"></script>
    <style>
    </style>
</head>

<body class="bkgimg">
    <lable>选择文章地址文件：</lable><input type="file" id="chapters_hreff">
    <input type="button" id="b4" value="读取全部文件">

    <script>
        var c_href = ''
        var wait = false
        function readAsText(tem,id){
            var t = tem;
            console.log('------',t)
            file = document.getElementById(id).files[0];
            reader = new FileReader();
            reader.readAsText(file)
            reader.onload = function(f){
                jsArr = JSON.stringify(this.result);
                tem = jsArr.replace(/"/g,'');
                tem = tem,split("--#--");
                if(t=='chapters_href'){
                    c_href = tem;
                    console.log('进来了吗？',c_href)
                }
            }
        }
        document.getElementById('b4').addEventListener('click',function(){
            wait = true
            if(wait){
            readAsText('chapters_href','chapters_hreff');
            console.log('这里呢',c_href)
            }
        })

    </script>
</body>

</html>

条件语句，只有在条件成立时才会去执行，如果条件不成立，你那个c_href自然是没有定义。