# unicorn/prefer-number-coercion

> Require `Number()` instead of `parseFloat()` and base-10 `parseInt()`

`parseFloat` and `parseInt` read as many characters as they can and ignore the rest, so `parseFloat("12px")` is `12` and `parseInt("1e3", 10)` is `1`. `Number()` converts the whole string, so bad input gives `NaN`, which you can check for.

The rule reports `parseFloat(value)` and `parseInt(value, 10)`, including when they're written as `Number.parseFloat` and `Number.parseInt`. `parseInt` with no radix or with another radix isn't reported.

`--fix` doesn't change the code, because the result can differ. `--fix-suggestions` rewrites it to `Number(value)`, or to `Math.trunc(Number(value))` for `parseInt`.

{/* Generated by src/codegen/lint-rule-docs.ts. Do not edit this section. */}

## Configure

Off by default. To turn it on:

```toml bunfig.toml
[lint.rules]
"unicorn/prefer-number-coercion" = "error" # or "warn"
```

{/* End of the generated section. */}

## Examples

Reported:

{/* bad {"count": 2} */}
```js
const price = parseFloat(input.value);
const quantity = Number.parseInt(form.quantity, 10);
```

Not reported:

{/* good */}
```js
const price = Number(input.value);
const quantity = Math.trunc(Number(form.quantity));

const color = parseInt(hex, 16);
const page = parseInt(query.page);
```

## When not to use it

The results differ. `Number("")` is `0` where `parseFloat("")` is `NaN`, and `Number("12px")` is `NaN`. If you parse strings with a unit or other text after the number, keep `parseFloat`.