【JavaScript】- Count the number of occurrences of a string (using object)

Requirement: have a string, get the number of occurrences of each character in it

What is the format of the result? {a:4,s:5,f:7}

let str = 'asdfasdfasdfsadfasdfz'
    // 字符串的本质是字符数组

    console.dir(str)

    let obj = {}

    for (let i = 0; i < str.length; i++) {
      // 判断当前对象中是否有当前遍历到的key,如果有，说明它已经存在过，我们应该将数量+1，如果没有就新增这个key,设置数量为1
      let key = str[i]
      if (obj[key]) {
        // 如果存在过，数量+1
        obj[key] = obj[key] + 1
      } else {
        // 如果没有存在，就第一次出现，数量为1
        obj[key] = 1
      }
    }

    console.log(obj)