---
url: /docs/guide/usage/linter/rules/eslint/no-plusplus.md
---

### What it does

Disallow the unary operators `++` and `--`.

### Why is this bad?

Because the unary `++` and `--` operators are subject to automatic semicolon insertion, differences in whitespace
can change the semantics of source code. For example, these two code blocks are not equivalent:

```js
var i = 10;
var j = 20;

i++;
j;
// => i = 11, j = 20
```

```js
var i = 10;
var j = 20;

i;
++j;
// => i = 10, j = 21
```

### Examples

Examples of **incorrect** code for this rule:

```js
var x = 0;
x++;
var y = 0;
y--;
for (let i = 0; i < l; i++) {
  doSomething(i);
}
```

Examples of **correct** code for this rule:

```js
var x = 0;
x += 1;
var y = 0;
y -= 1;
for (let i = 0; i < l; i += 1) {
  doSomething(i);
}
```

## Configuration

This rule accepts a configuration object with the following properties:

### allowForLoopAfterthoughts

type: `boolean`

default: `false`

Whether to allow `++` and `--` in for loop afterthoughts.

## How to use

## Version

This rule was added in v0.9.5.

## References