//Try this code

const countSubStr = (str, search) => {
    let arrStr = str.split('');
    let i = 0, count = 0;

    while(i < arrStr.length){
        let subStr = i + search.length + 1 <= arrStr.length ?
                  arrStr.slice(i, i+search.length).join('') :
                  arrStr.slice(i).join('');
        if(subStr === search){
            count++;
            arrStr.splice(i, search.length);
        }else{
            i++;
        }
    }
    return count;
  }

/** Function that count occurrences of a substring in a string;
 * @param {String} string               The string
 * @param {String} subString            The sub string to search for
 * @param {Boolean} [allowOverlapping]  Optional. (Default:false)
 *
 * @author Vitim.us https://gist.github.com/victornpb/7736865
 * @see Unit Test https://jsfiddle.net/Victornpb/5axuh96u/
 * @see https://stackoverflow.com/a/7924240/938822
 */
function occurrences(string, subString, allowOverlapping) {

    string += "";
    subString += "";
    if (subString.length <= 0) return (string.length + 1);

    var n = 0,
        pos = 0,
        step = allowOverlapping ? 1 : subString.length;

    while (true) {
        pos = string.indexOf(subString, pos);
        if (pos >= 0) {
            ++n;
            pos += step;
        } else break;
    }
    return n;
}

用法

occurrences("foofoofoo", "bar"); //0

occurrences("foofoofoo", "foo"); //3

occurrences("foofoofoo", "foofoo"); //1

允许重叠

occurrences("foofoofoo", "foofoo", true); //2

比赛：

  foofoofoo
1 `----´
2    `----´

单元测试

https://jsfiddle.net/Victornpb/5axuh96u/

基准

我做了一个基准测试，我的功能超过了10倍比gumbo发布的regexp匹配函数更快。在我的测试中字符串长度为25个字符。字符“o”出现2次。我在Safari中执行了1000 000次。Safari 5.1基准>执行总时间：5617ms（正则表达式）基准测试>执行总时间：881毫秒（我的功能快6.4倍）Firefox 4基准>执行总时间：8547毫秒（Rexep）基准测试>总执行时间：634毫秒（我的功能更快13.5倍）编辑：我所做的更改缓存的子字符串长度为字符串添加了类型转换。添加了可选的“allowOverlapping”参数修复了“”空子字符串大小写的正确输出。

Gist

https://gist.github.com/victornpb/7736865

我们可以使用jssplit函数，它的长度减1就是出现的次数。

var temp = "This is a string.";
alert(temp.split('is').length-1);

正则表达式（global的缩写）中的g表示搜索整个字符串，而不仅仅是查找第一个出现的字符串。此匹配是两次：

var temp=“这是一个字符串。”；var count=（temp.match（/is/g）| |[]）.length；console.log（计数）；

如果没有匹配项，则返回0：

var temp=“Hello World！”；var count=（temp.match（/is/g）| |[]）.length；console.log（计数）；

参数：ustring：超集字符串countChar：子字符串

一个计算JavaScript中子字符串出现次数的函数：

函数subStringCount（ustring，countChar）{var correspCount=0；var corresp=false；变量量=0；var prevChar=空；对于（var i=0；i！=ustring.length；i++）{如果（ustring.charAt（i）==countChar.charAt（0）&&corresp==false）{corresp=真；correspCount+=1；如果（correspCount==countChar.length）{数量+=1；corresp=false；correspCount=0；}prevChar=1；}否则如果（ustring.charAt（i）==countChar.charAt（prevChar）&&corresp==true）{correspCount+=1；如果（correspCount==countChar.length）{数量+=1；corresp=false；correspCount=0；prevChar=空；}其他{prevChar+=1；}}其他{corresp=false；correspCount=0；}} 回报金额；}console.log（subStringCount（“Hello World，Hello World”，“ll”））；

基于@Vittim.us的上述回答。我喜欢他的方法给我的控制，使其易于扩展，但我需要添加不区分大小写的功能，并将匹配限制在支持标点符号的整个单词中。（例如，“洗澡”是指“洗澡”，而不是“洗澡”）

标点正则表达式来自：https://stackoverflow.com/a/25575009/497745（如何使用正则表达式从JavaScript字符串中删除所有标点符号？）

function keywordOccurrences(string, subString, allowOverlapping, caseInsensitive, wholeWord)
{

    string += "";
    subString += "";
    if (subString.length <= 0) return (string.length + 1); //deal with empty strings

    if(caseInsensitive)
    {            
        string = string.toLowerCase();
        subString = subString.toLowerCase();
    }

    var n = 0,
        pos = 0,
        step = allowOverlapping ? 1 : subString.length,
        stringLength = string.length,
        subStringLength = subString.length;

    while (true)
    {
        pos = string.indexOf(subString, pos);
        if (pos >= 0)
        {
            var matchPos = pos;
            pos += step; //slide forward the position pointer no matter what

            if(wholeWord) //only whole word matches are desired
            {
                if(matchPos > 0) //if the string is not at the very beginning we need to check if the previous character is whitespace
                {                        
                    if(!/[\s\u2000-\u206F\u2E00-\u2E7F\\'!"#$%&\(\)*+,\-.\/:;<=>?@\[\]^_`{|}~]/.test(string[matchPos - 1])) //ignore punctuation
                    {
                        continue; //then this is not a match
                    }
                }

                var matchEnd = matchPos + subStringLength;
                if(matchEnd < stringLength - 1)
                {                        
                    if (!/[\s\u2000-\u206F\u2E00-\u2E7F\\'!"#$%&\(\)*+,\-.\/:;<=>?@\[\]^_`{|}~]/.test(string[matchEnd])) //ignore punctuation
                    {
                        continue; //then this is not a match
                    }
                }
            }

            ++n;                
        } else break;
    }
    return n;
}

如果发现错误或改进，请随时修改和重构此答案。