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{{alias}}( ...f )
Function composition.
Returns a composite function. Starting from the right, the composite
function evaluates each function and passes the result as the first argument
of the next function. The result of the leftmost function is the result
of the whole.
The last argument for each provided function is a `next` callback which
should be invoked upon function completion. The callback accepts two
arguments:
- `error`: error argument
- `result`: function result
If a composed function calls the `next` callback with a truthy `error`
argument, the composite function suspends execution and immediately calls
the `done` callback for subsequent `error` handling.
Execution is *not* guaranteed to be asynchronous. To guarantee asynchrony,
wrap the `done` callback in a function which either executes at the end of
the current stack (e.g., `nextTick`) or during a subsequent turn of the
event loop (e.g., `setImmediate`, `setTimeout`).
Only the rightmost function is explicitly permitted to accept multiple
arguments. All other functions are evaluated as binary functions.
The function will throw if provided fewer than two input arguments.
Parameters
----------
f: ...Function
Functions to compose.
Returns
-------
out: Function
Composite function.
Examples
--------
> function a( x, next ) {
... setTimeout( onTimeout, 0 );
... function onTimeout() {
... next( null, 2*x );
... }
... };
> function b( x, next ) {
... setTimeout( onTimeout, 0 );
... function onTimeout() {
... next( null, x+3 );
... }
... };
> function c( x, next ) {
... setTimeout( onTimeout, 0 );
... function onTimeout() {
... next( null, x/5 );
... }
... };
> var f = {{alias}}( c, b, a );
> function done( error, result ) {
... if ( error ) {
... throw error;
... }
... console.log( result );
... };
> f( 6, done )
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See Also
--------
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