JS实现驼峰字符串转下划线字符串的三种方法

function toUnderline(str) {
  return str.replace(/([A-Z])/g, '_$1').toLowerCase();
}
 
console.log(toUnderline('yiZhiXiaoKeLeYa')); // 输出 'yi_zhi_xiao_ke_le_ya'
console.log(toUnderline('myCode')); // 输出 'my_code'

function toUnderline(str) {
  let result = '';
  for (let i = 0; i < str.length; i++) {
    if (str[i] === str[i].toUpperCase()) {
      result += '_' + str[i].toLowerCase();
    } else {
      result += str[i];
    }
  }
  return result;
}
console.log(toUnderline('yiZhiXiaoKeLeYa')); // 输出 'yi_zhi_xiao_ke_le_ya'
console.log(toUnderline('myCode')); // 输出 'my_code'

function toUnderline(str) {
  if (str.length <= 1) {
    return str.toLowerCase();
  }
  let firstChar = str[0];
  if (firstChar === firstChar.toUpperCase()) {
    firstChar = '_' + firstChar.toLowerCase();
  }
  return firstChar + toUnderline(str.slice(1));
}
 
console.log(toUnderline('yiZhiXiaoKeLeYa')); // 输出 'yi_zhi_xiao_ke_le_ya'
console.log(toUnderline('myCode')); // 输出 'my_code'