SOURCE

function a(val){
    val = val.split(/_|\s+/)
    val.forEach((v,i)=>{
        v = v.toLocaleLowerCase()
        v = v.replace(v[0],v[0].toUpperCase())
        val[i] = v
    })
    val = val.join('_')
    return val
}
let test = 'My  a22  acco     un1t'
console.log(a(test))