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{{alias}}( obj, [options,] transform, done )
Maps keys from one object to a new object having the same values.
When invoked, `transform` is provided a maximum of four arguments:
- `key`: object key
- `value`: object value corresponding to `key`
- `obj`: the input object
- `next`: a callback to be invoked after processing an object `key`
The actual number of provided arguments depends on function length. If
`transform` accepts two arguments, `transform` is provided:
- `key`
- `next`
If `transform` accepts three arguments, `transform` is provided:
- `key`
- `value`
- `next`
For every other `transform` signature, `transform` is provided all four
arguments.
The `next` callback accepts two arguments:
- `error`: error argument
- `key`: transformed key
If a `transform` function calls the `next` callback with a truthy `error`
argument, the function suspends execution and immediately calls the `done`
callback for subsequent `error` handling.
The key returned by a transform function should be a value which can be
serialized as an object key.
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 only maps own properties. Hence, the function does not map
inherited properties.
The function shallow copies key values.
Key iteration and insertion order are *not* guaranteed.
Parameters
----------
obj: Object
Source object.
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 property sequentially.
Default: false.
options.thisArg: any (optional)
Execution context.
transform: Function
Transform function. Returned values specify the keys of the output
object.
done: Function
A callback invoked either upon processing all own properties or upon
encountering an error.
Examples
--------
// Basic usage:
> function transform( key, value, next ) {
... setTimeout( onTimeout, value );
... function onTimeout() {
... next( null, key+':'+value );
... }
... };
> function done( error, out ) {
... if ( error ) {
... throw error;
... }
... console.log( out );
... };
> var obj = { 'a': 1, 'b': 2 };
> {{alias}}( obj, transform, done )
{ 'a:1': 1, 'b:2': 2 }
// Limit number of concurrent invocations:
> function transform( key, value, next ) {
... setTimeout( onTimeout, value );
... function onTimeout() {
... next( null, key+':'+value );
... }
... };
> function done( error, out ) {
... if ( error ) {
... throw error;
... }
... console.log( out );
... };
> var opts = { 'limit': 2 };
> var obj = { 'a': 1, 'b': 2, 'c': 3 };
> {{alias}}( obj, opts, transform, done )
{ 'a:1': 1, 'b:2': 2, 'c:3': 3 }
// Process sequentially:
> function transform( key, value, next ) {
... setTimeout( onTimeout, value );
... function onTimeout() {
... next( null, key+':'+value );
... }
... };
> function done( error, out ) {
... if ( error ) {
... throw error;
... }
... console.log( out );
... };
> var opts = { 'series': true };
> var obj = { 'a': 1, 'b': 2, 'c': 3 };
> {{alias}}( obj, opts, transform, done )
{ 'a:1': 1, 'b:2': 2, 'c:3': 3 }
{{alias}}.factory( [options,] transform )
Returns a function which maps keys from one object to a new object having
the same values.
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 property sequentially.
Default: false.
options.thisArg: any (optional)
Execution context.
transform: Function
Transform function. Returned values specify the keys of the output
object.
Returns
-------
out: Function
A function which maps keys from one object to a new object having the
same values.
Examples
--------
> function transform( key, value, next ) {
... setTimeout( onTimeout, value );
... function onTimeout() {
... next( null, key+':'+value );
... }
... };
> var opts = { 'series': true };
> var f = {{alias}}.factory( opts, transform );
> function done( error, out ) {
... if ( error ) {
... throw error;
... }
... console.log( out );
... };
> var obj = { 'a': 1, 'b': 2, 'c': 3 };
> f( obj, done )
{ 'a:1': 1, 'b:2': 2, 'c:3': 3 }
> obj = { 'beep': 'boop' };
> f( obj, done )
{ 'beep:boop': 'beep' }
See Also
--------
|
