I understand this is an old frequent question, but I still find it confusing and am not exactly sure.
What is the different purposes and performance implications in every type of loop?
--Generic for i loop
for i = 1,#container do
print(i,container[i])
end
--Generic loop
for index,value in container do
print(index,value)
end
--pairs loop
for index,value in pairs(container) do
print(index,value)
end
--ipairs loop
for index,value in ipairs(container) do
print(index,value)
end
--table library functions
table.foreach(container, print)
table.foreachi(container, print)
Age old question, TL;DR: Use Ipairs for numerical arrays 1,2,3,…#table and pairs for dictionaries.
performance doesn’t matter in this case you won’t notice it so it’s negligible, also has the same conclusion TL;DR: Use Ipairs for numerical arrays 1,2,3,…#table and pairs for dictionaries.
Now this is the only interesting thing I found:
This is just a Luau shortcut for both ipairs and pairs.
The problem I see is backwards compatibility with Lua and also the fact that it’s vague readability and it doesn’t tell you if you are iterating through a dictionary or array, or both.
In Lua, to iterate over a table you need to use an iterator like next or a function that returns one like pairs or ipairs . In Luau, you can simply iterate over a table:
The default iteration order for tables is specified to be consecutive for elements 1..#t and unordered after that, visiting every element; similarly to iteration using pairs , modifying the table entries for keys other than the current one results in unspecified behavior.
