# trycatchAsync
> If a function does not return an error, invoke a callback with the function result; otherwise, invoke a callback with a value `y`.
## Usage
```javascript
var trycatchAsync = require( '@stdlib/utils/async/try-catch' );
```
#### trycatchAsync( x, y, done )
If a function `x` does not return an error, invokes a `done` callback with the function result; otherwise, invokes a `done` callback with a value `y`.
```javascript
var randu = require( '@stdlib/random/base/randu' );
function x( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
if ( randu() > 0.5 ) {
return clbk( null, 1.0 );
}
clbk( new Error( 'oops' ) );
}
}
function done( error, result ) {
if ( error ) {
console.log( error.message );
}
console.log( result );
}
trycatchAsync( x, -1.0, done );
```
The function `x` is provided a single argument:
- `clbk`: callback to invoke upon function completion
The callback accepts two arguments:
- `error`: error object
- `result`: function result
The `done` callback is invoked upon function completion and is provided two arguments:
- `error`: error object
- `result`: either the result of `x` or the provided value `y`
If the function `x` does not return a truthy `error` argument, the `error` argument provided to the `done` callback is `null`. If `x` does return a truthy `error` argument, the `done` callback is invoked with both the `error` and the provided value `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 trycatchAsync = require( '@stdlib/utils/async/try-catch' );
var i;
function next() {
trycatchAsync( x, 'beep', done );
}
function x( clbk ) {
setTimeout( onTimeout, 0 );
function onTimeout() {
if ( randu() > 0.9 ) {
return clbk( null, 'BOOP' );
}
clbk( new Error( 'oops' ) );
}
}
function done( error, result ) {
if ( error ) {
console.log( error.message );
}
i += 1;
console.log( result );
if ( i < 100 ) {
return next();
}
}
i = 0;
next();
```