# Grip


[A take on Go Style Error Handling In JavaScript](https://dev.to/nesterow/a-take-on-go-style-error-handling-in-javascript-577)

Simplified result/error handling for JavaScript.
Grip always returns a consistent call result ready to be handled.
It makes the control flow similar to that of Golang, but doesn't force you to make additional null checks or create transitional variables to hold error results.


Instead of returning a nullish error, Grip always returns a consistent status object:

```javascript
const [value, status] = grip(callable) // or {value, status}

if (status.of(MySpecificError)) {
  // handle specific error
}

if (status.fail()) {
  // handle any error
}
```

The call result is better than tuple:

```javascript
const result = grip(callable)

if (result.of(MySpecificError)) {
  // handle specific error
}

if (result.fail()) {
  // handle any error
}

console.log(result.value) // result[0]
```

Grip also works with Promises, functions that return promises, generators and async generators.

## Install

```bash
bun add github:nesterow/grip # or pnpm
```

## Usage

The `grip` function accepts a function or a promise and returns a result with return value and status.
The result can be hadled as either an object or a tuple.

```javascript
import { grip } from '@nesterow/grip';
```

## Handle result as an object

The result can be handled as an object: `{value, status, Ok(), Fail(), Of(type)}`

```javascript
const res = await grip(
  fetch('https://api.example.com')
);

if (res.fail()) {
    // handle error
}

const json = await grip(
  res.value.json()
);

if (json.of(SyntaxError)) {
    // handle parse error
}

```

## Handle result as a tuple

The result can also be received as a tuple if you want to handle errors in Go'ish style:

```javascript
const [res, fetchStatus] = await grip(
  fetch('https://api.example.com')
);

if (fetchStatus.fail()) {
    // handle  error
}

const [json, parseStatus] = await grip(
  res.json()
);

if (parseStatus.of(SyntaxError)) {
    // handle parse error
}
```

## Handle functions

Grip can also handle functions:

```javascript
const [result, status] = grip(() => "ok");
// result = "ok"

const [result1, status1] = grip(() => {
  if (1) throw new Error("error")
});
// result1 = null
// status.Of(Error) = true
```

## Handle generators

Generators can be handled using the `Iter()` method:

```javascript
const res = grip(async function* () {
  for (let i = 0; i < 3; i++) {
    if (i == 2) throw new Error("2");
    yield i;
  }
});
for await (let [value, status] of res.iter()) {
  if (status.of(Error)) {
    // handle error properly
    break;
  }
  // typeof value === "number"
  console.log(value)
}
```

## License

MIT