for (let i = 0; i < list.length; i++) {
  list[i] = list[i] * 2;
}
Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request.

### Instruction:
How can the following code be improved for readability?

### Input:
for(let i = 0; i < list.length; i++)
{
  list[i] *=2
}

### Response:
for (let i = 0; i < list.length; i++) {
  list[i] = list[i] * 2;
}
assistant

The provided code can be improved for readability by extracting a separate function to calculate the value and then applying the operation inside the loop. Here's the improved code:

```javascript
function doubleValue(element) {
  return element * 2;
}

for (let i = 0; i < list.length; i++) {
  list[i] = doubleValue(list[i]);
}
```

In this code:

*   We define a separate function `doubleValue` that takes an element and returns its doubled value.
*   We apply the operation inside the loop by calling `doubleValue` on each element in the list.
*   This approach improves readability by separating the calculation from the loop, making it easier to understand what the code is doing.

However, this solution assumes that the input list `list` is already populated with numbers. If the list is empty or contains non-numeric values, the `doubleValue` function will throw an error. To handle this, you can add a check at the beginning of the function to return `undefined` or throw a custom error if the input is invalid:

```javascript
function doubleValue(element) {
  if (typeof element!== 'number') {
    throw new Error('Input must be a number');
  }
  return element * 2;
}
```

Alternatively, you can use the spread operator (`[...list]`) to create a copy of the array, and then apply the operation on the copy instead of the original array:

```javascript
const copy = [...list];
for (let i = 0; i < list.length; i++) {
  list[i] = copy[i] * 2;
}
```