<pre><code class="language-javascript">/**
 * @param {string} str
 * @returns {string | string[]}
 *
 * */
function count(str) {
  let obj={};
  for(let i=0; i&lt;str.length; i++){
    if(obj[str[i]]){
      obj[str[i]]+=1;
    }
    else {
      obj[str[i]]=1;
    }
  }
  let max = Math.max(...Object.values(obj)), res=[];
  for(let [key,value] of Object.entries(obj)){
    if(value === max) {
      res.push(key);
    }
  }
  
  return res.length &gt; 1 ? res : res[0];
}
</code></pre>


This is my accepted solution

Given a non-empty string, return the most frequently ocurring character. If there are multiple characters with same occurrance, return an array of the…

146. implement Array.prototype.reduce()

146. Array.prototype.reduce() を実装してください

146. 实现Array.prototype.reduce()

144. serialize and deserialize data types not supported in JSON

144. JSON data type以外のdata typeをserialize/deserializeする

144. 序列化和反序列化JSON不支持的数据类型

145. most frequently occurring character

145. 最も頻繁に出現する文字

145. 最多重复出现的字符