TypeScript hashmap dictionary interface

Question

I m new to using TypeScript and I m trying to implement a hashmap dictionary interface  So far I have  export interface IHash        details  string    string       I m having some trouble understanding what exactly this syntax means  If I were to do var x   IHash       how would I go about adding accessing the data

User · Accepted Answer

Just as a normal js object   let myhash  IHash           myhash  somestring      value     set  let value   myhash  somestring      get   There are two things you re doing with  indexer  string    string    tell TypeScript that the object can have any string-based key that for all key entries the value MUST be a string type       You can make a general dictionary with explicitly typed fields by using  key  string   any     e g  age must be number  while name must be a string - both are required  Any implicit field can be any type of value    As an alternative  there is a Map class    let map   new Map lt object  string gt       let key   new Object     map set key   value    map get key      return  value    This allows you have any Object instance  not just number string  as the key    Although its relatively new so you may have to polyfill it if you target old systems

User · Answer

The most simple and the correct way is to use Record type  Record lt string  string gt  const myVar   Record lt string  string gt         key1   val1      key2   val2

User · Answer

var x   IHash       x  key1      value1   x  key2      value2    console log x  key1        outputs value1  console log x  key2        outputs value2   If you would like to then iterate through your dictionary  you can use   Object keys x  forEach  key    gt   console log x key        Object keys returns all the properties of an object  so it works nicely for returning all the values from dictionary styled objects   You also mentioned a hashmap in your question  the above definition is for a dictionary style interface  Therefore the keys will be unique  but the values will not   You could use it like a hashset by just assigning the same value to the key and its value   if you wanted the keys to be unique and with potentially different values  then you just have to check if the key exists on the object before adding to it   var valueToAdd    one   if  x valueToAdd      x valueToAdd    valueToAdd    or you could build your own class to act as a hashset of sorts   Class HashSet    private var keys  IHash         private var values  string            public Add key  string       if  keys key          values push key         keys key    key               public GetValues           slicing the array will return it by value so users cannot accidentally        start playing around with your array     return values slice

[typescript] TypeScript hashmap/dictionary interface

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