从字符串中抓取第一个字母 [英] Grab first letter from string

问题描述

我有这个代码：

JS

 var a = document.getElementById("quantity");
   var quantity = a.value;

HTML

<select id="quantity" name=''>
  <option title='Option 2' value='2 people'>2 people</option>
  <option title='Option 3' value='3 people'>3 people</option>
  <option title='Option 4' value='4 people'>4 people</option>
  <option title='Option 3' value='5 people'>5 people</option>
  <option title='Option 4' value='6 people'>6 people</option>
</select>

我不能只改变HTML的HTML。如何让它输出第一个字符，所以我实际得到的是一个数字（2,3,4,5或6）。

I can't change the HTML only the JS. How do I get it to output the first char, so what I am actually getting out is a number (either 2,3,4,5 or 6).

I试过这个，但它打破了剧本：

I tried this but it broke the script:

var a = document.getElementById("quantity");
var quantity = a.substring(0,1);

推荐答案

你很接近。你想使用 substring（） 与 值：

You were close. You want to use substring() with value:

var a = document.getElementById("quantity");
a.addEventListener("change", function() {
  var quantity = a.value.substring(0, 1);
  console.log(quantity);
});

<select id="quantity" name=''>
  <option title='Option 2' value='2 people'>2 people</option>
  <option title='Option 3' value='3 people'>3 people</option>
  <option title='Option 4' value='4 people'>4 people</option>
  <option title='Option 3' value='5 people'>5 people</option>
  <option title='Option 4' value='6 people'>6 people</option>
</select>

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