## Subtraction Assignment

`-=`

symbol is used for subtraction assignment operator

subtraction assignment operator takes two operands, subtracts the value in left operand with that of the right operand and assigns the result back to the left operand

```
a -= 5 //equivalent to a = a -+ 5
a -= b //equivalent to a = a - b
```

## Examples

1. subtraction assign `a`

with 5

```
var a = 4;
a -= 5;
console.log(a);
```

2. subtract `b`

from `a`

and assign the result back to `a`

```
var b = 7;
var a = 4;
a -= b;
console.log(a);
```