@stdlib/utils
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Standard utilities.
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{{alias}}( fcn, predicate, done[, thisArg] )
Invokes a function while a test condition is true.
The condition is evaluated *after* executing the provided function; thus,
`fcn` *always* executes at least once.
The function to invoke is provided two arguments:
- i: iteration number (starting from zero).
- next: a callback which must be invoked before proceeding to the next
iteration.
The first argument of the `next` callback is an `error` argument. If `fcn`
calls the `next` callback with a truthy `error` argument, the function
suspends execution and immediately calls the `done` callback for subsequent
`error` handling.
The predicate function is provided two arguments:
- i: iteration number (starting from one).
- clbk: a callback indicating whether to invoke `fcn`.
The `clbk` function accepts two arguments:
- error: error argument.
- bool: test result.
If the test result is truthy, the function continues invoking `fcn`;
otherwise, the function invokes the `done` callback.
The `done` callback is invoked with an `error` argument and any arguments
passed to the final `next` callback.
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`).
Parameters
----------
fcn: Function
The function to invoke.
predicate: Function
The predicate function which indicates whether to continue invoking a
function.
done: Function
Callback to invoke upon completion.
thisArg: any (optional)
Execution context for the invoked function.
Examples
--------
> function fcn( i, next ) {
... setTimeout( onTimeout, i );
... function onTimeout() {
... next( null, 'boop'+i );
... }
... };
> function predicate( i, clbk ) { clbk( null, i < 5 ); };
> function done( error, result ) {
... if ( error ) {
... throw error;
... }
... console.log( result );
... };
> {{alias}}( fcn, predicate, done )
boop: 4
See Also
--------