1、首先需要新建一个HTML文件,用于承载JS。
![](https://iknow-pic.cdn.bcebos.com/a50f4bfbfbedab64523eed13f936afc378311e90?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
2、然后需要按照图示代码在HTML的body中,定义JS,并定义一个变量。
![](https://iknow-pic.cdn.bcebos.com/023b5bb5c9ea15ce83a140dab8003af33b87b292?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
3、然后需要按照图示代码加入indeOf()方法,用来查看被查询字符串第一次返回的位置。
![](https://iknow-pic.cdn.bcebos.com/4bed2e738bd4b31ce86b346889d6277f9f2ff88a?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
4、然后需要保存文件,并在浏览器查看当前输出。返回值为:6,表明被查询的字符串'baidu'首次出现的索引位置为6。
![](https://iknow-pic.cdn.bcebos.com/8435e5dde71190ef9153320cc01b9d16fcfa60bd?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
5、然后需要按照图示代码继续实用IF语句结合indexOf()方法,由于找不到被查询的字符串,则会返回值为-1,以此为条件,进行判断。
![](https://iknow-pic.cdn.bcebos.com/2f738bd4b31c8701d1231235297f9e2f0608ff48?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
6、保存文件,并在浏览器执行,由于不存在被检索的字符串,所以返回值为-1,通过以上步骤即完成了判断对象是否是字符串。
![](https://iknow-pic.cdn.bcebos.com/d439b6003af33a87533ea0c9c85c10385243b596?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)