[javascript] Declare an array in TypeScript

I'm having trouble either declaring or using a boolean array in Typescript, not sure which is wrong. I get an undefined error. Am I supposed to use JavaScript syntax or declare a new Array object?

Which one of these is the correct way to create the array?

private columns = boolean[];
private columns = [];
private columns = new Array<boolean>();

How would I initialize all the values to be false?

How would I access the values, can I access them like, columns[i] = true;..?

this is how you can create an array of boolean in TS and initialize it with false:

var array: boolean[] = [false, false, false]

or another approach can be:

var array2: Array<boolean> =[false, false, false] 

you can specify the type after the colon which in this case is boolean array

Specific type of array in typescript

export class RegisterFormComponent 
{
     genders = new Array<GenderType>();   // Use any array supports different kind objects

     loadGenders()
     {
        this.genders.push({name: "Male",isoCode: 1});
        this.genders.push({name: "FeMale",isoCode: 2});
     }
}

type GenderType = { name: string, isoCode: number };    // Specified format

Few ways of declaring a typed array in TypeScript are

const booleans: Array<boolean> = new Array<boolean>();
// OR, JS like type and initialization
const booleans: boolean[] = [];

// or, if you have values to initialize 
const booleans: Array<boolean> = [true, false, true];
// get a vaue from that array normally
const valFalse = booleans[1];

let arr1: boolean[] = [];

console.log(arr1[1]);

arr1.push(true);