TypeScript namespace explanation

// validation.ts
// Create a namespace named Validation through namespace namespace Validation {
    // Define a regular expression const isLetterReg = /^[A-Za-z]+$/
    // Here we define a regular expression. The difference from the previous one is that this regular expression is exported through export const isNumberReg = /^[0-9]+$/
    // Export a method export const checkLetter = (text: any) => {
        return isLetterReg.test(text)
    }
}

// index.ts
/// <reference path='validation.ts' />
let isLetter = Validation.checkLetter('text')
const reg = Validation.isNumberReg
console.log(isLetter)
console.log(reg)

tsc --outFile src/index.js index.ts

//Create a namespace named Validation through namespace var Validation;
(function (Validation) {
    // Define a regular expression var isLetterReg = /^[A-Za-z]+$/;
    // Here we define a regular expression. The difference from the previous one is that this regular expression is exported through export. Validation.isNumberReg = /^[0-9]+$/;
    // Export a method Validation.checkLetter = function (text) {
        return isLetterReg.test(text);
    };
})(Validation || (Validation = {}));
/// <reference path='validation.ts' />
var isLetter = Validation.checkLetter('text');
var reg = Validation.isNumberReg;
console.log(isLetter);
console.log(reg);

// LetterValidation.ts
namespace Validation {
    export const isLetterReg = /^[A-Za-z]+$/
    export const checkLetter = (text: any) => {
        return isLetterReg.test(text)
    }
}

// NumberValidation.ts
namespace Validation {
    export const isNumberReg = /^[0-9]+$/
    export const checkNumber = (text: any) => {
        return isNumberReg.test(text)
    }
}

// index.ts
/// <reference path="./LetterValidation.ts"/>
/// <reference path="./NumberValidation.ts"/>
let isLetter = Validation.checkLetter('text')
const reg = Validation.isNumberReg
console.log(isLetter)

tsc --outFile src/index.js index.ts

// LetterValidation.ts
var Validation;
(function (Validation) {
    Validation.isLetterReg = /^[A-Za-z]+$/;
    Validation.checkLetter = function (text) {
        return Validation.isLetterReg.test(text);
    };
})(Validation || (Validation = {}));
// NumberValidation.ts
var Validation;
(function (Validation) {
    Validation.isNumberReg = /^[0-9]+$/;
    Validation.checkNumber = function (text) {
        return Validation.isNumberReg.test(text);
    };
})(Validation || (Validation = {}));
/// <reference path="./LetterValidation.ts"/>
/// <reference path="./NumberValidation.ts"/>
var isLetter = Validation.checkLetter('text');
var reg = Validation.isNumberReg;
console.log(isLetter);

import q = xyz

// Define a namespace namespace Shapes {
    // Define a subnamespace in the namespace and export it export namespace Polygons {
        export class Triangle {}
        export class Square {}
    }
}
// Rename the exported subnamespace to polygons using import syntax
import polygons = Shapes.Polygons
// Instantiate the Square class from the exported namespace let sq = new polygons.Square()