ES2015 chronometer

chronometer.js

'use strict'
let it=(function*(){
    let i=1
    while(1){
        yield new Promise((resolve)=>{
            setTimeout(()=>{
                resolve(i++)
            },1000)
        })
    }
}());
(function c(f){
    let r=it.next(),v=r.value
    if(r.done){
        return v
    }else{
        return v
        .then(f)
        .then(()=>c(f))
    }
}((n)=>console.log(`${n} seconds passed`)))