Undefined typescript object properties

Question

this my code

file.js

const channel = {},
arr = [string,string,string];
for(let i = 0;i < arr.length;i++ ){
    channel[arr[i]] = "Amo" //equal string value
}

An array contains only string values. example ["a","b","c","n"]. How can I write this code in typescript ?

Answer 1

The only difference between JS and TS is the concept of strongly typing your code. In this case, you want to migrate this code from JS to TS, you shouldn't need to do anything as the TS transpiler will be able to infer the types of the variables. If you do wants to enforce the type for the variables, you can do:

interface channelObj {
    [key: string]: string
} // This is called index signature and is useful for typing object key-value
const channel: channelObj = {},
arr: string[] = [string, ...];
for(let i = 0;i < arr.length;i++ ){
    channel[arr[i]] = "Amo" //equal string value
}