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{{alias}}( collection, [options,] fcn, done )
Invokes a function once for each element in a collection and updates a
collection in-place, iterating from right to left.
When invoked, `fcn` is provided a maximum of four arguments:
- `value`: collection value
- `index`: collection index
- `collection`: the input collection
- `next`: a callback to be invoked after processing a collection `value`
The actual number of provided arguments depends on function length. If `fcn`
accepts two arguments, `fcn` is provided:
- `value`
- `next`
If `fcn` accepts three arguments, `fcn` is provided:
- `value`
- `index`
- `next`
For every other `fcn` signature, `fcn` is provided all four arguments.
The `next` callback accepts two arguments:
- `error`: error argument
- `result`: value used to update the collection
If a provided function calls the `next` callback with a truthy `error`
argument, the function suspends execution and immediately calls the `done`
callback for subsequent `error` handling. Note, however, that the function
may have mutated an input collection during prior invocations, resulting in
a partially mutated collection.
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`).
The function does not support dynamic collection resizing.
The function does not skip `undefined` elements.
Parameters
----------
collection: Array|TypedArray|Object
Input collection over which to iterate. If provided an object, the
object must be array-like (excluding strings and functions).
options: Object (optional)
Function options.
options.limit: integer (optional)
Maximum number of pending invocations. Default: Infinity.
options.series: boolean (optional)
Boolean indicating whether to process each collection element
sequentially. Default: false.
options.thisArg: any (optional)
Execution context.
fcn: Function
The function to invoke for each element in a collection.
done: Function
A callback invoked either upon processing all collection elements or
upon encountering an error.
Examples
--------
// Basic usage:
> function fcn( value, index, next ) {
... setTimeout( onTimeout, value );
... function onTimeout() {
... console.log( value );
... next( null, value*index );
... }
... };
> function done( error, collection ) {
... if ( error ) {
... throw error;
... }
... console.log( collection === arr );
... console.log( collection );
... };
> var arr = [ 1000, 2500, 3000 ];
> {{alias}}( arr, fcn, done )
1000
2500
3000
true
[ 0, 2500, 6000 ]
// Limit number of concurrent invocations:
> function fcn( value, index, next ) {
... setTimeout( onTimeout, value );
... function onTimeout() {
... console.log( value );
... next( null, value*index );
... }
... };
> function done( error, collection ) {
... if ( error ) {
... throw error;
... }
... console.log( collection === arr );
... console.log( collection );
... };
> var opts = { 'limit': 2 };
> var arr = [ 1000, 2500, 3000 ];
> {{alias}}( arr, opts, fcn, done )
2500
3000
1000
true
[ 0, 2500, 6000 ]
// Process sequentially:
> function fcn( value, index, next ) {
... setTimeout( onTimeout, value );
... function onTimeout() {
... console.log( value );
... next( null, value*index );
... }
... };
> function done( error, collection ) {
... if ( error ) {
... throw error;
... }
... console.log( collection === arr );
... console.log( collection );
... };
> var opts = { 'series': true };
> var arr = [ 1000, 2500, 3000 ];
> {{alias}}( arr, opts, fcn, done )
3000
2500
1000
true
[ 0, 2500, 6000 ]
{{alias}}.factory( [options,] fcn )
Returns a function which invokes a function once for each element in a
collection and updates a collection in-place, iterating from right to left.
Parameters
----------
options: Object (optional)
Function options.
options.limit: integer (optional)
Maximum number of pending invocations. Default: Infinity.
options.series: boolean (optional)
Boolean indicating whether to process each collection element
sequentially. Default: false.
options.thisArg: any (optional)
Execution context.
fcn: Function
The function to invoke for each element in a collection.
Returns
-------
out: Function
A function which invokes a function for each element in a collection.
Examples
--------
> function fcn( value, index, next ) {
... setTimeout( onTimeout, value );
... function onTimeout() {
... console.log( value );
... next( null, value*index );
... }
... };
> var opts = { 'series': true };
> var f = {{alias}}.factory( opts, fcn );
> function done( error, collection ) {
... if ( error ) {
... throw error;
... }
... console.log( collection === arr );
... console.log( collection );
... };
> var arr = [ 1000, 2500, 3000 ];
> f( arr, done )
3000
2500
1000
true
[ 0, 2500, 6000 ]
> arr = [ 1000, 1500, 2000 ];
> f( arr, done )
2000
1500
1000
true
[ 0, 1500, 4000 ]
See Also
--------
|
