# Replace Multiple Instances of Pattern in JavaScript

> How to replace multiple instances of a pattern in JavaScript with a regular expression.

Source: https://curiouslychase.com/engineering/replace-multiple-instances-of-pattern-in-javascript/

If you want to replace a pattern multiple times with the JavaScript `replace` method, you have to use a regular expression with the global flag.

Replacing **the first found instance** is achieved with the following:

```js
"this is a string".replace(" ", "-");
```

Result:

```
"this-is a string"
```

When calling the `replace` method with a string as the first argument, it will only replace the first instance with the replace value (in this case `"-"`).

Replacing **all found instances** is achieved with a regular expression and global flag:

```js
"this is a string".replace(/ /g, "-");
```

Result:

```
"this-is-a-string"
```

When the `replace` method with a regular expression and the global flag, it will replace all instances with the replace value.