> For the complete documentation index, see [llms.txt](https://aup.nomi.dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://aup.nomi.dev/the-language/control-flow/for-loop.md). # For loop ## Simple loop ### Syntax `for , ` * `init` is an **initializer**, explained [below](/the-language/control-flow/for-loop.md#the-initializer) * `end` is an expression, the value which initial variable iterates through to * `body` is a statement ### The initializer It could be: #### A variable declaration ```javascript for var i = 0 ... for let j = 0 ... ``` Use #### A assign expression ```javascript var i = 0 for i ... ``` If the target vairable in the assignment is not defined, it will be defined by the **let** keyword implicitly. ```javascript for j = 0 ... // like: for let j = 0 ... ``` ### Examples #### Counting numbers ```lua for i = 1, 10 { puts i } ``` #### Printing even numbers ```lua for i = 0, 20 { if i % 2 == 0 { puts i } } ``` #### Counting down ```lua for i = 20, 1 { puts i } ``` ## C-style loop But no parenthese, comma instead of semicolon. ### Syntax `for , , ` * `init` is loop initializer, it could be an expression * `cond` is loop condition, an expression * `updater` is an expression, which is executed after the loop body ### Examples #### Basic ```c for i = 0, i < 5, i++ { // do something } ``` #### Without updater ```javascript for i = 0, i < 5, { i++ // own updater } ``` {% hint style="warning" %} If the last comma is removed, the loop becomes [**Simple loop**](/the-language/control-flow/for-loop.md#simple-loop). {% endhint %} ## For-each loop Iterating through an array, map. ### Syntax `for [, ] : ` * `first` - the first variable * `second` - the second variable (optional) * `expr` - an expression to be evaluated, value must be a map or an array ### Examples With an array: ```javascript var arr = [1, 2, 3] for v, i : arr { puts v, i // value - index } ``` Just use `for v : arr` to get the value only. ```javascript for v : arr { puts v } ``` With a map: ```javascript var map = { a: 4, b: 5, c: 6 } for k, v : map { puts k, v // key - value } ``` Depend on the implementation, the key - value pairs may not in input order. So the output of above example could be: ``` a 4 b 5 c 6 ``` ... or ``` b 5 c 6 a 4 ``` Like array, just get the key only: ```javascript for k : map { puts k } ``` ## Infinite loop #### Pure ```javascript for { // Do something } ``` #### With initializer ```javascript for i = 1 { puts i++ } ```