join(): turning a list into text with a chosen separator

In a few sentences

In brief

The method returns a string and does not add a separator after the last item.

Useful to know

join() connects the text representation of the elements to a selected delimiter. For example, ["Sofia", "Plovdiv"].join(" / ") gives "Sofia / Plovdiv". In an empty array, the result is an empty string . [1]

Use it to display a simple list when the data is already prepared. Do not take it as a complete CSV generator: values with commas, quotation marks or new lines require rules for escaping. Selecting a separator is a visual task; safely serializing into a specific file format is another.

Sources

For further detail and to check the information:

[1] MDN — Array.join ↗