如何在 JavaScript 中检查元音？
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How do I check for vowels in JavaScript?
提问by Max
I'm supposed to write a function that takes a character (i.e. a string of length 1) and returns true if it is a vowel, false otherwise. I came up with two functions, but don't know which one is better performing and which way I should prefer. The one with RegEx is way simpler but I am unsure whether I should try to avoid using RegEx or not?
我应该编写一个函数，它接受一个字符（即长度为 1 的字符串），如果它是元音则返回 true，否则返回 false。我想出了两个功能，但不知道哪个性能更好，我应该更喜欢哪种方式。使用 RegEx 的方式更简单，但我不确定是否应该尽量避免使用 RegEx？
Without RegEx:
没有正则表达式：
function isVowel(char) {
if (char.length == 1) {
var vowels = new Array("a", "e", "i", "o", "u");
var isVowel = false;
for (e in vowels) {
if (vowels[e] == char) {
isVowel = true;
}
}
return isVowel;
}
}
With RegEx:
使用正则表达式：
function isVowelRegEx(char) {
if (char.length == 1) {
return /[aeiou]/.test(char);
}
}
回答by Raynos
I think you can safely say a for loop is faster.
我认为您可以安全地说 for 循环更快。
I do admit that a regexp looks cleaner in terms of code. If it's a real bottleneck then use a for loop, otherwise stick with the regular expression for reasons of "elegance"
我承认正则表达式在代码方面看起来更清晰。如果这是一个真正的瓶颈，则使用 for 循环，否则出于“优雅”的原因坚持使用正则表达式
If you want to go for simplicity then just use
如果你想简单，那么只需使用
function isVowel(c) {
return ['a', 'e', 'i', 'o', 'u'].indexOf(c.toLowerCase()) !== -1
}
回答by RobG
Lots of answers available, speed is irrelevant for such small functions unless you are calling them a few hundred thousand times in a short period of time. For me, a regular expression is best, but keep it in a closure so you don't build it every time:
有很多可用的答案，速度对于这样的小函数来说无关紧要，除非您在短时间内调用它们几十万次。对我来说，正则表达式是最好的，但把它放在一个闭包中，这样你就不会每次都构建它：
Simple version:
简单版：
function vowelTest(s) {
return (/^[aeiou]$/i).test(s);
}
More efficient version:
更高效的版本：
var vowelTest = (function() {
var re = /^[aeiou]$/i;
return function(s) {
return re.test(s);
}
})();
Returns trueif sis a single vowel (upper or lower case) and falsefor everything else.
返回trueifs是单个元音（大写或小写）和false其他所有内容。
回答by Emmerman
cycles, arrays, regexp... for what? It can be much quicker :)
循环、数组、正则表达式……为了什么？它可以更快:)
function isVowel(char)
{
return char === 'a' || char === 'e' || char === 'i' || char === 'o' || char === 'u' || false;
}
回答by Buhake Sindi
This is a rough RegExp function I would have come up with (it's untested)
这是我想出的一个粗略的 RegExp 函数（未经测试）
function isVowel(char) {
return /^[aeiou]$/.test(char.toLowerCase());
}
Which means, if (char.length == 1 && 'aeiou' is contained in char.toLowerCase()) then return true.
这意味着，if (char.length == 1 && 'aeiou' is contained in char.toLowerCase()) then return true。
回答by José Salgado
function findVowels(str) {
return str.match(/[aeiou]/ig);
}
findVowels('abracadabra'); // 'aaaaa'
Basically it returns all the vowels in a given string.
基本上它返回给定字符串中的所有元音。
回答by cwallenpoole
Personally, I would define it this way:
就个人而言，我会这样定义：
function isVowel( chr ){ return 'aeiou'.indexOf( chr[0].toLowerCase() ) !== -1 }
You could also use ['a','e','i','o','u']and skip the length test, but then you are creating an array each time you call the function. (There are ways of mimicking this via closures, but those are a bit obscure to read)
您也可以使用['a','e','i','o','u']并跳过长度测试，但是每次调用该函数时都会创建一个数组。（有一些方法可以通过闭包来模仿这一点，但这些方法读起来有点难懂）
回答by H?vard
function isVowel(char)
{
if (char.length == 1)
{
var vowels = "aeiou";
var isVowel = vowels.indexOf(char) >= 0 ? true : false;
return isVowel;
}
}
Basically it checks for the index of the character in the string of vowels. If it is a consonant, and not in the string, indexOfwill return -1.
基本上它会检查元音字符串中字符的索引。如果是辅音，并且不在字符串中，indexOf则返回 -1。
回答by Intellidroid
I kind of like this method which I think covers all the bases:
我有点喜欢这种方法，我认为它涵盖了所有基础：
const matches = str.match(/aeiou/gi];
return matches ? matches.length : 0;
回答by Penny Liu
I created a simplified version using Array.prototype.includes(). My technique is similar to @Kunle Babatunde.
我使用Array.prototype.includes()创建了一个简化版本。我的技术类似于@Kunle Babatunde。
const isVowel = (char) => ["a", "e", "i", "o", "u"].includes(char);
console.log(isVowel("o"), isVowel("s"));回答by Kunle Babatunde
//function to find vowel
const vowel = (str)=>{
//these are vowels we want to check for
const check = ['a','e','i','o','u'];
//keep track of vowels
var count = 0;
for(let char of str.toLowerCase())
{
//check if each character in string is in vowel array
if(check.includes(char)) count++;
}
return count;
}
console.log(vowel("hello there"));
