有没有更好的方法在文本块中添加换行符而不是在每个项目之后添加
？(Is there a better way to add line-breaks in a block of text than just putting
after every item?)

 在您的示例中， map和forEach之间的本质区别在于forEach对原始数组元素进行操作，而map显式返回一个新的数组。 
 
 使用forEach您将对原始数组中的每个元素进行一些操作（可选择更改）。 forEach方法运行您为每个元素提供的函数，但不返回任何内容（ undefined ）。 另一方面， map遍历数组，对每个元素应用一个函数，并将结果作为新的数组发出 。 
 
 forEach的“副作用”是原来的数组正在改变。 使用map “无副作用”意味着，在惯用语中，原始数组元素不改变; 新数组是原始数组中每个元素的一对一映射 - 映射变换是您提供的函数。 
 
 没有数据库涉及的事实并不意味着您不必对数据结构进行操作，毕竟这是数据结构中任何语言的编程之一。 对于你最后一个问题，你的数组不仅可以包含数字，而且可以包含对象，字符串，函数等。 

The essential difference between map and forEach in your example is that forEach operates on the original array elements, whereas map explicitly returns a new array as a result. 
 
With forEach you are taking some action with -- and optionally changing -- each element in the original array. The forEach method runs the function you provide for each element, but returns nothing (undefined). On the other hand, map walks through the array, applies a function to each element, and emits the result as a new array. 
 
The "side effect" with forEach is that the original array is being changed. "No side effect" with map means that, in idiomatic usage, the original array elements are not changed; the new array is a one-to-one mapping of each element in the original array -- the mapping transform being your provided function.
 
The fact that there's no database involved does not mean that you won't have to operate on data structures, which, after all, is one of the essences of programming in any language. As for your last question, your array can contain not only numbers, but objects, strings, functions, etc.