repl.txt (2135B)
1 2 {{alias}}( ...fcn ) 3 Returns a pipeline function. 4 5 Starting from the left, the pipeline function evaluates each function and 6 passes the result as the first argument of the next function. The result of 7 the rightmost function is the result of the whole. 8 9 The last argument for each provided function is a `next` callback which 10 should be invoked upon function completion. The callback accepts two 11 arguments: 12 13 - `error`: error argument 14 - `result`: function result 15 16 If a provided function calls the `next` callback with a truthy `error` 17 argument, the pipeline function suspends execution and immediately calls the 18 `done` callback for subsequent `error` handling. 19 20 Execution is *not* guaranteed to be asynchronous. To guarantee asynchrony, 21 wrap the `done` callback in a function which either executes at the end of 22 the current stack (e.g., `nextTick`) or during a subsequent turn of the 23 event loop (e.g., `setImmediate`, `setTimeout`). 24 25 Only the leftmost function is explicitly permitted to accept multiple 26 arguments. All other functions are evaluated as binary functions. 27 28 The function will throw if provided fewer than two input arguments. 29 30 Parameters 31 ---------- 32 fcn: ...Function 33 Functions to evaluate in sequential order. 34 35 Returns 36 ------- 37 out: Function 38 Pipeline function. 39 40 Examples 41 -------- 42 > function a( x, next ) { 43 ... setTimeout( onTimeout, 0 ); 44 ... function onTimeout() { 45 ... next( null, 2*x ); 46 ... } 47 ... }; 48 > function b( x, next ) { 49 ... setTimeout( onTimeout, 0 ); 50 ... function onTimeout() { 51 ... next( null, x+3 ); 52 ... } 53 ... }; 54 > function c( x, next ) { 55 ... setTimeout( onTimeout, 0 ); 56 ... function onTimeout() { 57 ... next( null, x/5 ); 58 ... } 59 ... }; 60 > var f = {{alias}}( a, b, c ); 61 > function done( error, result ) { 62 ... if ( error ) { 63 ... throw error; 64 ... } 65 ... console.log( result ); 66 ... }; 67 > f( 6, done ) 68 3 69 70 See Also 71 -------- 72