string-overlap-one-on-another npm package

Idea

In essence,

//           aaa
//      +  bbb      (negative offset of 2 means it's pushed to the left by 2 places)
//         -----
//      =  bbbaa

The main function overlap() is imported like this:

It’s a function which takes three input arguments:

Input argument	Type	Obligatory	Description
	`str1` Type: String Obligatory: yes
`str1`	String	yes	The string which will be put “under” `str2`

	`str2` Type: String Obligatory: yes
`str2`	String	yes	The string which will be put “over” `str1`

	`opts` Type: Plain object Obligatory: no
`opts`	Plain object	no	Optional Options Object.

The Optional Options Object has the following shape:

Key	Type	Default	Description
	`offset` Type: Positive or negative integer or zero Default: `0`
`offset`	Positive or negative integer or zero	`0`	It instructs to offset the top string by this many characters to the right (if a positive number) or to the left (if a negative number). The default value is zero.

	`offsetFillerCharacter` Type: String Default: `" "` (a single space)
`offsetFillerCharacter`	String	`" "` (a single space)	If the offset value (character amount to push left) pushes the `str2` outside the boundaries of `str1` and not even there’s no overlap, but there is a gap, this gap is formed out of these characters. The default is a single space.

Here are all defaults in one place for copying:

The function will return a string.

You can import defaults:

It's a plain object:

The main function calculates the options to be used by merging the options you passed with these defaults.

You can import version:

The algorithm is the following:

If one and only one of two input strings is zero-long, the other string is returned as a result.
If both input strings are empty, an empty string is returned.
If both input strings are non-empty, the result is second string overlaid on the first, considering the offset.