javascript - 表单以在 javascript 数组中查找值的位置

Question

我正在尝试创建一个只需要一个字母并在数组中找到它的位置（本质上是字母表）的表单。

我写了一些简单的代码：

var alphabet = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"];
var letter = "h";
var letterPosition = alphabet.indexOf(letter);

document.write(letterPosition);

演示基本功能。但是，我不确定如何将其放入 afunction get并使其var letter等于表单输入中的值。

我希望它返回数组中的位置，以便我可以编写一个循环（在 if/else 内），它将打印数组中输入值之后的所有值。

Answer 1

搭建一个demo http://jsbin.com/ijuco4

Answer 2

尝试：alphabet[alphabet.indexOf(letter)]或在您的代码中alphabet[letterPosition]

关于您提到的循环slice：使用该值，您可以使用该方法为您提供alphabet数组中剩余字符的子集（ergo：不需要循环来确定数组中的剩余元素）：

var subset = alphabet.slice(indexOf([a letter]));

只是为了节省你的打字时间：你也可以像这样声明你的字母数组：

var alphabet 'abcdefghijklmnopqrstuvwxyz'.split('');

Answer 3

不确定上下文，这是与页面一起加载（不涉及 AJAX）吗？我可能过于简单化了：

<input type="text" id="whichLetter" />
<script type="text/javascript">

function getLetterPosition(allLetters, letter)
{
  return allLetters.indexOf(letter);
}

var alphabet = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"];
var letter = document.getElementById("whichLetter").value;
var letterPosition = getLetterPosition(alphabet, letter);

</script>

我喜欢 JavaScript。

Answer 4

或者你可以做

let alphabetPosition = (text) => text.toUpperCase().replace(/[^A-Z]/g, '').split('').map(ch => ch.charCodeAt(0) - 64).join(' ');