My goal is start with an array
with null values than if an other
array has entries replace accordingly
just to do en example

```
const a = [...[null,null,null, null], ...[1,2,3,4]]

```

I want an array **[1,2,3,4]**

at start the second array could be also empty like

```
const a = [...[null,null,null, null], ...[]]

```

or

```
const a = [...[null,null,null, null], ...[1]]

```

and so on ....

```
const a = [null,null,null, null];
const b = [1,2,3];
const c = a.map((item,i)=> b[i] ? b[i] : a[i])

```

Is there a better way ?