simple calcalater in ts

calcalater.ts

type Operation="+"|"-"|"*"|"/"
function calcalater(a:Array<number>=[1,2,3],b:Array<number>=[5,2,3],operation:Operation='-'){
 let len=a.length>=b.length?a.length:b.length
 let res:Array<number>=[]

 for(let i=0;i<len;i++){
     let first
     let secand
if(operation==='+' ||operation==="-"){
 first=a[i]?a[i]:0
 secand=b[i]?b[i]:0
 let tow=operation==="+"?first+secand:first-secand
 res.push(tow)
 
}
else{
    first=a[i]?a[i]:1
 secand=a[i]?b[i]:1
  let tow=operation==="*"?first*secand:Math.floor(first/secand)
 res.push(tow)
}
     
 }
 return res

}


console.log(calcalater())