---
id: 587d7b88367417b2b2512b44
title: Write Arrow Functions with Parameters
challengeType: 1
---
## Description
Just like a regular function, you can pass arguments into an arrow function.
// doubles input value and returns it
const doubler = (item) => item * 2;
If an arrow function has a single argument, the parentheses enclosing the argument may be omitted.
// the same function, without the argument parentheses
const doubler = item => item * 2;
It is possible to pass more than one argument into an arrow function.
// multiplies the first input value by the second and returns it
const multiplier = (item, multi) => item * multi;
## Instructions
Rewrite the myConcat function which appends contents of arr2 to arr1 so that the function uses arrow function syntax.
## Tests
```yml
tests:
- text: User did replace var keyword.
testString: getUserInput => assert(!getUserInput('index').match(/var/g), 'User did replace var keyword.');
- text: myConcat should be a constant variable (by using const).
testString: getUserInput => assert(getUserInput('index').match(/const\s+myConcat/g), 'myConcat should be a constant variable (by using const).');
- text: myConcat should be a function
testString: assert(typeof myConcat === 'function', 'myConcat should be a function');
- text: myConcat() returns the correct array
testString: assert(() => { const a = myConcat([1], [2]); return a[0] == 1 && a[1] == 2; }, 'myConcat() returns the correct array');
- text: function keyword was not used.
testString: getUserInput => assert(!getUserInput('index').match(/function/g), 'function keyword was not used.');
```
## Challenge Seed
```js
var myConcat = function(arr1, arr2) {
"use strict";
return arr1.concat(arr2);
};
// test your code
console.log(myConcat([1, 2], [3, 4, 5]));
```
## Solution
```js
const myConcat = (arr1, arr2) => {
"use strict";
return arr1.concat(arr2);
};
// test your code
console.log(myConcat([1, 2], [3, 4, 5]));
```