JavaScript中每个循环的计数

发表时间：2022-07-21 00:49:19 阅读：108

I am trying to find the total number of a specific character is in string.

for example

myString = &quot; this is my string &quot;;

I want to count how many "s" is in myString. I tried the following:

function myFunction(a, b) {
  const letters = b.split(&quot;&quot;);
  console.log(letters);

  letters.forEach(letter =&gt; {
    let letterCount = 0;
    if(letter === a) {
      console.log(&quot;yes&quot;)
      letterCount++;       
    }
    console.log(letterCount);      
  })
}

myFunction(&#39;s&#39;, &#39;this is my string&#39;) // Expected result: 3

🎖️ 优质答案

过滤器是实现这一点的正确方法.

'this is my string'.split('').filter(s => s === 's').length

您可以使用reduce获取所有字符的信息:

&lt!-开始代码段:js hide:false控制台:true babel:false--&gt

&lt!-语言:lang js--&gt

function countRepeatedChars(str) {
  return str.split('').reduce((acc, val) => {
    acc[val] = acc[val] ? ++acc[val] : 1

    return acc
  }, {})
}

console.log(countRepeatedChars('dfgdfghdfghdfhdfhwefw'))

&lt!-结束代码段--&gt

Using a simple regular expression

function escapeRegExp(string) { // from https://stackoverflow.com/a/6969486/12101554
    return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); // $& means the whole matched string
}

const myFunction = (match, str) => str.match(new RegExp(escapeRegExp(match), "g"))?.length ?? 0;

console.log(myFunction('s', 'this is my string')) // Expected result: 3
console.log(myFunction('s', 'thi i my tring')) // Expected result: 0
console.log(myFunction('a', 'john has five apples and six bananas')) // Expected result: 6

您可以使用拆分执行以下操作:

&lt!-开始代码段:js hide:false控制台:true babel:false--&gt

&lt!-语言:lang js--&gt

myString = " this is my string ";
console.log(myString.split('s').length - 1);

&lt!-结束代码段--&gt

更简单的方法是使用regexp进行计数.

&lt!-开始代码段:js hide:false控制台:true babel:false--&gt

&lt!-语言:lang js--&gt

myString = " Sure this iss my string ";
console.log(myString.match(/(s)/ig).length);

&lt!-结束代码段--&gt