第180题(2020-03-26)：实现一个方法，将传入对象的下划线命名方式全部换为驼峰式(考虑递归的场景)。比如

[qappleh]

// before
const obj = {
  first_name: 'chen'
}

// after
const obj = {
  firstName: 'chen'
}

[Leo-wwj]

const replaceUpper = (val, char='_') => {
var arr = val.split('');
var index = arr.indexOf(char)
arr.splice(index, 2, arr[index+1].toUpperCase())
var newVal = arr.join('')
return newVal
}

const filterUnderLine = (obj, char='_') => {
var arr = Object.keys(obj).filter(item => item.indexOf(char) !== -1);
arr.forEach(item => {
var before = typeof obj[item] === 'object'? filterUnderLine(obj[item]) : obj[item];
var key = replaceUpper(item)
obj[key] = before;
delete obj[item]
})
return obj
}