Difference between += and =+ in javascript

Question

I want to know why after running the third line of code the result of `a` is 5? ``` a = 10; b = 5; a =+ b; ```

Accepted Answer

Awkward formatting:

```
a =+ b;
```

is equivalent to:

```
a = +b;
```

And `+b` is just a fancy way of casting `b` to number, like here:

```
var str = "123";
var num = +str;
```

You probably wanted:

```
a += b;
```

being equivalent to:

```
a = a + b;
```

Solution