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