alias.d.ts

type Uuid = string;

boilerplate.ts

import * as ts from "typescript";

const file = ts.createSourceFile("source.ts", "", ts.ScriptTarget.ESNext, false, ts.ScriptKind.TS);
const printer = ts.createPrinter({ newLine: ts.NewLineKind.LineFeed });

dict.d.ts

interface Dict<T> {
  [key: string]: T;
}

dict.ts

import * as ts from "typescript";

const file = ts.createSourceFile("source.ts", "", ts.ScriptTarget.ESNext, false, ts.ScriptKind.TS);
const printer = ts.createPrinter({ newLine: ts.NewLineKind.LineFeed });

const dictValueIdentifier = ts.factory.createIdentifier("T");

const key = ts.factory.createParameterDeclaration(
  undefined,
  undefined,
  undefined,
  "key",
  undefined,
  ts.factory.createTypeReferenceNode("string")
);

const index = ts.factory.createIndexSignature(
  undefined,
  undefined,
  [key],
  ts.factory.createTypeReferenceNode(dictValueIdentifier)
);

const dictDecl = ts.factory.createInterfaceDeclaration(
  undefined,
  undefined,
  "Dict",
  [ts.factory.createTypeParameterDeclaration(dictValueIdentifier)],
  undefined,
  [index]
);

const result = printer.printNode(ts.EmitHint.Unspecified, dictDecl, file);
console.log(result);

poco.ts

import * as ts from "typescript";

const file = ts.createSourceFile("source.ts", "", ts.ScriptTarget.ESNext, false, ts.ScriptKind.TS);
const printer = ts.createPrinter({ newLine: ts.NewLineKind.LineFeed });

const readonlyModifier = ts.factory.createModifier(ts.SyntaxKind.ReadonlyKeyword);

const idProp = ts.factory.createPropertySignature(
  [readonlyModifier],
  "id",
  undefined,
  ts.factory.createTypeReferenceNode("string")
);

const nameProp = ts.factory.createPropertySignature(
  [readonlyModifier],
  "name",
  undefined,
  ts.factory.createTypeReferenceNode("string")
);

const commentProp = ts.factory.createPropertySignature(
  [readonlyModifier],
  "comment",
  ts.factory.createToken(ts.SyntaxKind.QuestionToken),
  ts.factory.createTypeReferenceNode("string")
)

const pricesProp = ts.factory.createPropertySignature(
  [readonlyModifier],
  "prices",
  undefined,
  ts.factory.createArrayTypeNode(ts.factory.createTypeReferenceNode("number"))
)

const productDecl = ts.factory.createInterfaceDeclaration(
  undefined,
  undefined,
  "Product",
  undefined,
  undefined,
  [idProp, nameProp, commentProp, pricesProp]
);

const declareModifier = ts.factory.createModifier(ts.SyntaxKind.DeclareKeyword);
const storeNamespaceBlock = ts.factory.createModuleBlock([productDecl]);
const storeNamespaceDecl = ts.factory.createModuleDeclaration(
  undefined,
  [declareModifier],
  ts.factory.createIdentifier("Store"),
  storeNamespaceBlock,
  ts.NodeFlags.Namespace
);

const result = printer.printNode(ts.EmitHint.Unspecified, storeNamespaceDecl, file);
console.log(result);

store.d.ts

declare namespace Store {
  interface Product {
    readonly id: string;
    readonly name: string;
    readonly comment?: string;
    readonly prices: number[];
  }
}

string_or_number.d.ts

type StringOrNumber = string | number;

type_alias.ts

import * as ts from "typescript";

const file = ts.createSourceFile("source.ts", "", ts.ScriptTarget.ESNext, false, ts.ScriptKind.TS);
const printer = ts.createPrinter({ newLine: ts.NewLineKind.LineFeed });

const stringTypeReference = ts.factory.createTypeReferenceNode("string");
const uuidDecl = ts.factory.createTypeAliasDeclaration(
  undefined, // decorators
  undefined, // modifiers
  ts.factory.createIdentifier("Uuid"), // name
  undefined, // type parameters
  stringTypeReference // aliased type
);

const result = printer.printNode(ts.EmitHint.Unspecified, uuidDecl, file);
console.log(result);

union.ts

import * as ts from "typescript";

const file = ts.createSourceFile("source.ts", "", ts.ScriptTarget.ESNext, false, ts.ScriptKind.TS);
const printer = ts.createPrinter({ newLine: ts.NewLineKind.LineFeed });

const stringTypeReference = ts.factory.createTypeReferenceNode("string");
const numberTypeReference = ts.factory.createTypeReferenceNode("number");
const stringOrNumberTypeReference = ts.factory.createUnionTypeNode([
  stringTypeReference,
  numberTypeReference
]);

const stringOrNumberDecl = ts.factory.createTypeAliasDeclaration(
  undefined, // decorators
  undefined, // modifiers
  ts.factory.createIdentifier("StringOrNumber"), // name
  undefined, // type parameters 
  stringOrNumberTypeReference // aliased type
);

const result = printer.printNode(ts.EmitHint.Unspecified, stringOrNumberDecl, file);
console.log(result);