javascript - how to handle data type switching properly for pairs-CodePudding

let assume I have below list

1: Peter,
2: Mary,
3: Ken
...

I want to have a function switch which return like below

let value1 = switch("Peter") // return 1
let value2 = switch(3) // return "Ken"

I know I can create a stupid function like

const switch = (input) => {
  if(typeof(input) === string){...}
  else if(typeof(input) === number){...}
}

Just want to know if there're any data structures which can help to do it better, instead of creating the objects for storing those pairs

CodePudding user response：

You can use Object.entries for looking up the value and key at the same time

//cannot assign numbers as keys directly
const data = {
  "1": "Peter",
  "2": "Mary",
  "3": "Ken"
};

//`switch` is a programming language key for `switch/case`
//so I name the function `switchDataInPair` instead of `switch`
function switchDataInPair(input) {
  for (const [key, value] of Object.entries(data)) {
    //cannot use absolute check with `===`, because numbers are strings
    if (key == input) {
      return value
    }
    if (value == input) {
      return key
    }
  }
  return "Not defined"
}

console.log(switchDataInPair("Ken")) //3
console.log(switchDataInPair(1)) //"Peter"
console.log(switchDataInPair("Something")) //"Not defined"

CodePudding user response：

Assuming the list is ordered, you can just convert it into an Array and use indexOf

const arr= ["Peter","Mary", "Ken"];

/*Switch is a keyword in javascript, so best use a different variable name.*/
const switcher= (input) => {
  if(typeof(input) === "string")
  {
    const result= arr.indexOf(input);
    return ~result ? result : "not found";
    //above line is equivalent to result > -1 ? result : "not found"
  }
  else if(typeof(input) === "number")
  {
    return arr[input]
  }
}

console.log(switcher("Mary"));
console.log(switcher(1));