对象key的驼峰转下划线

[Sunny]

实现函数：将对象小驼峰式的属性名转下划线如：userName -> user_name

[beary]

function transform(str) {
  let res = "";
  for (let i = 0; i < str.length; i++) {
    if (str[i] >= "A" && str[i] <= "Z") {
      res += "_" + str[i].toLowerCase();
    } else {
      res += str[i];
    }
  }

  return res;
}
console.log(transform("strAbc"));

[kangkang123269]

str.replace(/([a-z])([A-Z])/g, '$1_$2').toLowerCase();

[veneno_o]

let userName = "userName";
userName = userName.replace(/([a-z])([A-Z])/g, function(text, $1, $2){
    return $1 + "_" + $2.toLowerCase();
})
console.log(userName)