# ifelseAsync
> If a predicate function returns a truthy value, return `x`; otherwise, return `y`.
## Usage
```javascript
var ifelseAsync = require( '@stdlib/utils/async/if-else' );
```
#### ifelseAsync( predicate, x, y, done )
If a `predicate` function returns a truthy value, returns `x`; otherwise, returns `y`.
```javascript
var randu = require( '@stdlib/random/base/randu' );
function predicate( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, randu() > 0.5 );
}
}
function done( error, result ) {
if ( error ) {
throw error;
}
console.log( result );
}
ifelseAsync( predicate, 1.0, -1.0, done );
```
The `predicate` function is provided a single argument:
- `clbk`: callback to invoke upon `predicate` function completion
The callback accepts two arguments:
- `error`: error object
- `bool`: condition used to determine whether to return `x` or `y`
The `done` callback is invoked upon function completion and is provided at most two arguments:
- `error`: error object
- `result`: either `x` or `y`
## Notes
- 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`).
## Examples
```javascript
var randu = require( '@stdlib/random/base/randu' );
var ifelseAsync = require( '@stdlib/utils/async/if-else' );
var i;
function next() {
ifelseAsync( predicate, 'BOOP', 'beep', done );
}
function predicate( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
clbk( null, randu() > 0.9 );
}
}
function done( error, result ) {
if ( error ) {
throw error;
}
i += 1;
console.log( result );
if ( i < 100 ) {
return next();
}
}
i = 0;
next();
```