<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
const price=(function(){
const tactics={
'100-10':function(price){return price-parseInt(price/100)*10},
'200-20':function(price){return price-Math.floor(price/200)*20},
'80%':function(price){return price*0.8}
}
function calculate(price,tactic){
if(!tactics[tactic]) return 'tactic not found'
return tactics[tactic](price)
}
calculate.add=function(tactic,action){
if(tactics[tactic]){
if(confirm(`replace ${tactic}`)){
tactics[tactic]=action
}
}
tactics[tactic]=action
}
calculate.remove=(tactic)=>{
if(!tactics[tactic]) return 'tactic not found'
delete tactics[tactic]
}
return calculate
})()
console.log(price(320,'100-10'))
</script>
</body>
</html>