ifdef

$$ifdef is a compile-time macro that keeps code when a define key is present and truthy.

IMPORTANT

To get macro autocomplete in TypeScript, add @remotex-labs/xBuild to types in tsconfig.json.

{
  "compilerOptions": {
    "types": [
      "node",
      "@remotex-labs/xBuild"
    ]
  }
}

Syntax

$$ifdef('DEFINE_NAME', valueOrCallback)

Arguments

Argument	Type	Required	Notes
defineName	string literal	Yes	Must be a string literal, ex: 'DEBUG'
valueOrCallback	unknown	Yes	Function, expression, or literal

Define Evaluation

$$ifdef is enabled only when the key exists in define and the value is truthy.

define: {
  DEBUG: true,        // enabled
  PROD: false,        // disabled
  LOG_LEVEL: 'info',  // enabled
  RETRIES: 0          // disabled
}

NOTE

To inspect real macro replacements, run build with --verbose or -v.

Examples

Variable macro (function transform)

Source:

const $$debug = $$ifdef('DEBUG', () => console.log('debug'));

Output when enabled:

function $$debug() { return console.log('debug'); }

Output when disabled:

undefined

Immediate-call shape (IIFE expression)

Source:

const $$value = $$ifdef('DEBUG', (name: string) => {
  return name + ' 42';
})('test');

Output when enabled:

const $$value = ((name: string) => {
  return name + ' 42';
})('test');

Output when disabled:

// The macro call expression is removed (empty replacement).
// Avoid this shape when the define may be falsy.

Standalone expression

Source:

function initDebug(): void {
  console.log('init debug');
}

$$ifdef('DEBUG', initDebug());

Output when enabled:

function initDebug(): void {
  console.log('init debug');
}

(() => { return initDebug(); })();

Output when disabled:

function initDebug(): void {
  console.log('init debug');
}

Exported typed function (complex example)

Source:

export const $$complexFunction = $$ifdef('DEBUG', (value: string, key: number) => {
  return `${value}-${key}`;
});

$$complexFunction('test', 42);

Output when enabled:

export function $$complexFunction(value: string, key: number) {
  return `${value}-${key}`;
}

$$complexFunction('test', 42);

Output when disabled:

// The macro call expression is removed (empty replacement).

5. Exported literals

Source:

export const $$feature = $$ifdef('FEATURE_X', true);
export const $$someValue = $$ifdef('FEATURE_X', 40);

Output when enabled:

export const $$feature = true;
export const $$someValue = 40;

Validation Rules

• $$ifdef requires exactly 2 arguments.
• The first argument must be a string literal.
• Invalid arg count throws a build error.
• Non-string first argument is not transformed.

Related

• ifndef: inverse behavior (keeps code when key is missing or falsy).