CustomFunction<sync>

CustomFunction<sync extends "sync" | "async">: ((args: Value[]) => PromiseOr<Value, sync>)

Type Parameters

sync extends “sync” | “async”

A CustomFunction<'sync'> must return synchronously, but in return it can be passed to compile and compileString in addition to compileAsync and compileStringAsync.

A CustomFunction<'async'> may either return synchronously or asynchronously, but it can only be used with compileAsync and compileStringAsync.

Type declaration

- (args: Value[]): PromiseOr<Value, sync>
- A callback that implements a custom Sass function. This can be passed to functions.
```
const result = sass.compile('style.scss', {
  functions: {
    "sum($arg1, $arg2)": (args) => {
      const arg1 = args[0].assertNumber('arg1');
      const value1 = arg1.value;
      const value2 = args[1].assertNumber('arg2')
          .convertValueToMatch(arg1, 'arg2', 'arg1');
      return new sass.SassNumber(value1 + value2).coerceToMatch(arg1);
    }
  }
});
```
  Throws
  any - This function may throw an error, which the Sass compiler will treat as the function call failing. If the exception object has a message property, it will be used as the wrapped exception's message; otherwise, the exception object's toString() will be used. This means it's safe for custom functions to throw plain strings.
  Parameters
  - args: Value[]
    
    An array of arguments passed by the function's caller. If the function takes arbitrary arguments, the last element will be a SassArgumentList.
  Returns PromiseOr<Value, sync>
  The function's result. This may be in the form of a Promise, but if it is the function may only be passed to compileAsync and compileStringAsync, not compile or compileString.