Yes, this example is taking an array of URLs like urlArray = ["a","b"] and joining it as part of another array with one URL like url1 = "c" Thus, the resultant array URLs = [url1, urlArray] yields ["c", ["a","b"]] an array whose first element is url1 and whose second element is urlArray, an array of URLs. The spread operator (triple dots) will return the elements from an array thus [url1, ...urlArray] yields ["c", "a", "b"] an array whose first element is url1 and whose other elements are those elements from urlArray. I hope this helps!