
The comma operator (`,`) used in the following form evaluates the left-hand side (`a`) and returns the value of the right-hand side (`b`):

```js
const c = (a, b);
```

We can use it to shorten codes in some cases.

### Shorten an if statement

```js
let result;
if (condition) {
    doSomething();
    result = value;
} else {
    result = other;
}

// Shorten version
const result = condition ? (doSomething(), value) : other;
```

### Shorten an arrow function

```js
const arrowFn = (arg) => {
    doSomething();
    return result;
};

// Shorten version
const arrowFn = (arg) => (doSomething(), result);
```

Here is a few examples of using the comma operator to [shorten](https://1loc.dev) arrow functions:

-   [Count the occurrences of array elements](https://1loc.dev/#count-the-occurrences-of-array-elements)

```js
const countOccurrences = (arr) => arr.reduce((p, c) => ((p[c] = ++p[c] || 1), p), {});

countOccurrences([2, 1, 3, 3, 2, 3]);
// { '1': 1, '2': 2, '3': 3 }
```

-   [Split an array into chunks](https://1loc.dev/#split-an-array-into-chunks)

```js
const chunk = (arr, s) => arr.reduce((a, e, i) => (i % s ? a[a.length - 1].push(e) : a.push([e]), a), []);

chunk([1, 2, 3, 4, 5, 6, 7, 8], 3);
// [[1, 2, 3], [4, 5, 6], [7, 8]]
```

### See also

-   [Log a variable in an arrow function](/log-a-variable-in-an-arrow-function.html)


Shorten codes with the comma operator

Shorten an if statement

Shorten an arrow function

See also