Waiting until static variable completes initialization in constructor - static

Question

If i have classes like the following:
export class ClassA{
static Alpha: string;
static Beta: string[];
constructor(jsonData: any){
ClassA.Alpha = jsonData.alpha;
ClassA.Beta = new Array<string>();
for(let i=0; i<jsonData.betaList.length; i++){
ClassA.Beta.push(jsonData.betaList[i]);
}
//do whatever it takes that takes a really long time
}
}
export function foo(list: string[]){
//something
}
and when i write a code like the following:
let dat = //whatever to parse a certain json file
new ClassA(dat);
foo(ClassA.Beta);
I want to make sure that the initialization of ClassA.Beta is finished before foo() is called. is it possible? or does Typescript automatically handle such cases already?

Answer 1

You can be sure foo() will be executed after ClassA constructor is finished. Unless it uses any kind of async calls (Promises, setTimeout, etc.).
Having said that I think that current design is not the best one. Do you really want to initialize class static properties each time the constructor is called?
The better approach would be to have separate static initialization logic into Init() static method and call it in the proper place of your application:
export class ClassA{
static Alpha: string;
static Beta: string[];
public static Init(jsonData: any): void
{
ClassA.Alpha = jsonData.alpha;
ClassA.Beta = new Array<string>();
for(let i=0; i<jsonData.betaList.length; i++)
{
ClassA.Beta.push(jsonData.betaList[i]);
}
//do whatever it takes that takes a really long time
}
constructor()
{
//Initialize instance members here. Not static
}
}
export function foo(list: string[])
{
//something
}
let dat = {};//whatever to parse a certain json file
ClassA.Init(dat);
foo(ClassA.Beta);
This approach will allow you later to make Init() return Promise to make your code async if you will need to.