# trythen
> If a function does not throw, return the function return value; otherwise, return the return value of a second function.
## Usage
```javascript
var trythen = require( '@stdlib/utils/try-then' );
```
#### trythen( x, y )
If a function `x` does not throw, returns the return value of `x`; otherwise, returns the return value of a second function `y`.
```javascript
function x1() {
return 1.0;
}
function x2() {
throw new Error( 'beep' );
}
function y() {
return -1.0;
}
var z = trythen( x1, y );
// returns 1.0
z = trythen( x2, y );
// returns -1.0
```
The function `y` is provided a single argument:
- `error`: the error thrown by `x`
```javascript
var randu = require( '@stdlib/random/base/randu' );
function x() {
if ( randu() < 0.5 ) {
throw new Error( 'beep' );
}
throw new TypeError( 'boop' );
}
function y( err ) {
if ( err instanceof TypeError ) {
return 'boops';
}
return 'beeps';
}
var z = trythen( x, y );
// returns
```
## Examples
```javascript
var randu = require( '@stdlib/random/base/randu' );
var ceil = require( '@stdlib/math/base/special/ceil' );
var repeatString = require( '@stdlib/string/repeat' );
var trythen = require( '@stdlib/utils/try-then' );
var z;
var i;
function x() {
if ( randu() < 0.9 ) {
throw new Error( 'BOOP' );
}
return repeatString( 'BOOP', ceil( randu()*3.0 ) );
}
function y() {
return repeatString( 'beep', ceil( randu()*5.0 ) );
}
for ( i = 0; i < 100; i++ ) {
z = trythen( x, y );
console.log( z );
}
```