TypeScript Import Equals

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External Module Import (require)

// Syntax
import alias = require("module-name");

// Example
import express = require("express");

• Type Preservation: Unlike a standard JavaScript const express = require("express"), the import = require() syntax imports both the runtime value and the associated TypeScript type definitions.
• Emission: When the TypeScript compiler (tsc) targets CommonJS, this syntax transpiles directly into a standard Node.js require() call: const express = require("express");.

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Internal Namespace Aliasing

namespace Application {
    export namespace Infrastructure {
        export class DatabaseConnection {
            connect() {}
        }
    }
}

// Syntax
import alias = Namespace.NestedNamespace.Symbol;

// Example
import DbConn = Application.Infrastructure.DatabaseConnection;

const conn = new DbConn();

• Dual Binding: The alias created by import = binds to both the type and the value of the referenced entity. You can use the alias in type annotations (let x: DbConn) or as a runtime value (new DbConn()).
• Type Erasure: TypeScript applies strict type erasure to namespace aliases. If the alias is used only in type positions (e.g., as an interface or type annotation), the compiler completely removes the import = statement from the emitted JavaScript.
• Value Emission: If the alias is used as a runtime value, the compiler emits a standard var assignment in the resulting JavaScript to maintain the reference:

// Emitted JavaScript
var DbConn = Application.Infrastructure.DatabaseConnection;
var conn = new DbConn();