---
id: 5d792533717672657b81aa69
title: Part 18
challengeType: 0
---
## Description
<section id='description'>
When defining an arrow function with a single argument, the parentheses can be omitted:
```js
const greeting = name => `Hello !`;
```
Define a function `highPrecedence` which takes a single argument `str` and returns it.
</section>
## Instructions
<section id='instructions'>
</section>
## Tests
<section id='tests'>
```yml
tests:
- text: See description above for instructions.
testString: assert(highPrecedence("a") === "a");
```
</section>
## Challenge Seed
<section id='challengeSeed'>
<div id='html-seed'>
```html
<script>
const infixToFunction = {
"+": (x, y) => x + y,
"-": (x, y) => x - y,
"*": (x, y) => x * y,
"/": (x, y) => x / y
};
const infixEval = (str, regex) =>
str.replace(regex, (_, arg1, fn, arg2) =>
infixToFunction[fn](parseFloat(arg1), parseFloat(arg2))
);
</script>
```
</div>
### Before Test
<div id='html-setup'>
```html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Spreadsheet</title>
<style>
#container {
display: grid;
grid-template-columns: 50px repeat(10, 200px);
grid-template-rows: repeat(11, 30px);
}
.label {
background-color: lightgray;
text-align: center;
vertical-align: middle;
line-height: 30px;
}
</style>
</head>
<body>
<div id="container">
<div></div>
</div>
```
</div>
### After Test
<div id='html-teardown'>
```html
</body>
</html>
```
</div>
</section>
## Solution
<section id='solution'>
```html
<script>
const infixToFunction = {
"+": (x, y) => x + y,
"-": (x, y) => x - y,
"*": (x, y) => x * y,
"/": (x, y) => x / y
};
const infixEval = (str, regex) =>
str.replace(regex, (_, arg1, fn, arg2) =>
infixToFunction[fn](parseFloat(arg1), parseFloat(arg2)));
const highPrecedence = str => str;
</script>
```
</section>