Create a simple line editor

JavaScript (ES6), 15 14 bytes

I don't understand why this is getting so many upvotes!

s=>prompt(s,s)

Saved a byte thanks to Adám's suggestion that I display the original input in the prompt.

f=
s=>prompt(s,s)
console.log(f("Edit this ..."))

read -ei "$*" t
echo "$t"

Sample run:

bash-4.3$ bash interactive.sh hello world
hello golfing world
hello golfing world

(Line 2 above was the interactive editing, line 3 the output of resulted text.)

⍞←⍞⋄⍞

This is a tradfn, so to use it, do

∇a
⍞←⍞⋄⍞
∇

And then call it by using a, after which you supply the starting string, and then you can edit the string.