The [mozilla docs](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp)

```js
const re = /ab+c/i; // literal notation
// OR
const re = new RegExp("ab+c", "i"); // constructor with string pattern as first argument
// OR
const re = new RegExp(/ab+c/, "i"); // constructor with regular expression literal as first argument
```