How to enforce datatype of key and value in map in JS-CodePudding

Let's say I'm creating a map like this:

let myMap = new Map();

We know that key and value both can be of any type. But I've a requirement where I need to enforce Integer for the key and String for the value.

For e.g.:

1 => 'Apple'
2 => 'Ball'
3 => 'Cat'

Any attempt to violate this rule should be checked at compile time itself. But I'm getting syntax errors when I try to do somewhat similar:

  let myMap = new Map<integer,string>();

Please help.

CodePudding user response：

Javascript dosn't have an integer type only number. Therefor you would need to define it like so.

 let myMap = new Map<number,string>();

You can define a setter in which you validate the key like so

Number.isInteger(data) // returns weither or not data is an int

CodePudding user response：

In Typescript, you can use:

 const myMap: Map<number, string> = new Map<number, string>();

Unfortunately you can't do this kind of check in Javascript.

CodePudding user response：

Javascript in itself doesn't provide any syntax to support generic classes

You can try writing using this class below, which extends Map.

class Map2 extends Map{

    constructor(keyType, valueType){
        super()
        this._keyType = keyType;
        this._valueType = valueType;
        
    }


    _matchesType(key,value){
        return (typeof(key) === this._keyType) && (typeof(value) === this._valueType);
    }


    set(key, value){
       if(!this._matchesType(key,value))
             throw 'Type Mismatch Exception';
       super.set(key,value)
    }

}

Then use Map2 instead of normal Map, with types in the constructor. Like this,

const m2 = new Map2('number', 'string');

m2.set(1,'apple');
m2.get(1); //returns 'apple'

m2.set('test', 'test value') // throws Type Mismatch Exception