---
source: crates/biome_formatter_test/src/snapshot_builder.rs
info: js/babel-plugins/throw-expressions.js
---

# Input

```js
// https://babeljs.io/docs/en/babel-plugin-proposal-throw-expressions

function test(param = throw new Error('required!')) {
  const test = param === true || throw new Error('Falsy!');
}

```


# Prettier differences

```diff
--- Prettier
+++ Biome
@@ -1,5 +1,8 @@
 // https://babeljs.io/docs/en/babel-plugin-proposal-throw-expressions
 
-function test(param = throw new Error("required!")) {
-  const test = param === true || throw new Error("Falsy!");
+function test(param = throw new Error('required!')
+)
+{
+  const test = param === true ||
+  throw new Error("Falsy!");
 }
```

# Output

```js
// https://babeljs.io/docs/en/babel-plugin-proposal-throw-expressions

function test(param = throw new Error('required!')
)
{
  const test = param === true ||
  throw new Error("Falsy!");
}
```

# Errors
```
throw-expressions.js:3:23 parse ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  × Expected an expression, or an assignment but instead found 'throw'.
  
    1 │ // https://babeljs.io/docs/en/babel-plugin-proposal-throw-expressions
    2 │ 
  > 3 │ function test(param = throw new Error('required!')) {
      │                       ^^^^^
    4 │   const test = param === true || throw new Error('Falsy!');
    5 │ }
  
  i Expected an expression, or an assignment here.
  
    1 │ // https://babeljs.io/docs/en/babel-plugin-proposal-throw-expressions
    2 │ 
  > 3 │ function test(param = throw new Error('required!')) {
      │                       ^^^^^
    4 │   const test = param === true || throw new Error('Falsy!');
    5 │ }
  
throw-expressions.js:3:33 parse ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  × expected `,` but instead found `Error`
  
    1 │ // https://babeljs.io/docs/en/babel-plugin-proposal-throw-expressions
    2 │ 
  > 3 │ function test(param = throw new Error('required!')) {
      │                                 ^^^^^
    4 │   const test = param === true || throw new Error('Falsy!');
    5 │ }
  
  i Remove Error
  
throw-expressions.js:3:38 parse ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  × expected `,` but instead found `(`
  
    1 │ // https://babeljs.io/docs/en/babel-plugin-proposal-throw-expressions
    2 │ 
  > 3 │ function test(param = throw new Error('required!')) {
      │                                      ^
    4 │   const test = param === true || throw new Error('Falsy!');
    5 │ }
  
  i Remove (
  
throw-expressions.js:3:51 parse ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  × Expected a function body but instead found ')'.
  
    1 │ // https://babeljs.io/docs/en/babel-plugin-proposal-throw-expressions
    2 │ 
  > 3 │ function test(param = throw new Error('required!')) {
      │                                                   ^
    4 │   const test = param === true || throw new Error('Falsy!');
    5 │ }
  
  i Expected a function body here.
  
    1 │ // https://babeljs.io/docs/en/babel-plugin-proposal-throw-expressions
    2 │ 
  > 3 │ function test(param = throw new Error('required!')) {
      │                                                   ^
    4 │   const test = param === true || throw new Error('Falsy!');
    5 │ }
  
throw-expressions.js:4:34 parse ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  × Expected an expression but instead found 'throw'.
  
    3 │ function test(param = throw new Error('required!')) {
  > 4 │   const test = param === true || throw new Error('Falsy!');
      │                                  ^^^^^
    5 │ }
    6 │ 
  
  i Expected an expression here.
  
    3 │ function test(param = throw new Error('required!')) {
  > 4 │   const test = param === true || throw new Error('Falsy!');
      │                                  ^^^^^
    5 │ }
    6 │ 
  

```