# Loop
Executes the appropriate loop type based on the provided attributes.
## Component Signature
```
```
### Attributes
| Atrribute | Type | Required | Description | Default |
| -------------------- | ------------ | -------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------- |
| `array` | `array` | `false` | An Array object to iterate over. When specified, the loop will process each element
in the array. Can be used with item and/or index attributes.
Example: \
| |
| `item` | `string` | `false` | Variable name to hold the current item value during iteration. Behavior varies by loop type:
- Array loops: Contains the current array element
- List loops: Contains the current list item
- Collection loops: Contains the current collection key
- Times loops: If no index specified, contains the current iteration number
Example: \
| |
| `index` | `string` | `false` | Variable name to hold the current index/position during iteration. Behavior varies by loop type:
- Array loops: Contains the 1-based array index
- Numeric range loops: Contains the current numeric value (required)
- File loops: Contains the current line content (required)
- Times loops: Contains the current iteration number
Example: \
| |
| `to` | `double` | `false` | End value for numeric range loops. The loop continues while the index value
has not exceeded this value (considering step direction). Required when using
numeric range loops with from and index.
Example: \
| |
| `from` | `double` | `false` | Starting value for numeric range loops. Defaults to 0 if not specified.
Used in conjunction with to and index for numeric iteration.
Example: \
| |
| `step` | `number` | `false` | Increment/decrement value for numeric range loops. Defaults to 1.
Positive values increment the index, negative values decrement.
Zero values are ignored to prevent infinite loops.
Example: \
| `1` |
| `file` | `string` | `false` | Absolute path to a text file to read line by line. Each iteration provides
one line of the file content in the index variable. The file
is automatically closed when the loop completes. Requires index attribute.
Example: \
| |
| `list` | `string` | `false` | A delimited string to process item by item. Each item becomes available
through the item or index variable. Use with
delimiters to specify custom separators.
Example: \
| |
| `delimiters` | `string` | `false` | Characters that separate items in the list attribute.
Defaults to comma (",") if not specified. Multiple delimiter characters
can be specified.
Example: \
| |
| `condition` | `function` | `false` | A function/closure that returns a boolean value. The loop continues
while this condition evaluates to true. The condition is evaluated
before each iteration.
Example: \
| |
| `query` | `any` | `false` | A Query object or variable name containing a query to iterate over.
Each iteration makes one row of the query available. Can be combined
with group for grouped processing, or startRow/
endRow for range constraints.
Example: \
| |
| `group` | `string` | `false` | Comma-separated list of query column names to group by. When specified,
the loop processes data in groups, executing the body once per group
change rather than once per row. Enables nested looping for hierarchical
data processing. Requires query attribute.
Example: \
| |
| `groupCaseSensitive` | `boolean` | `false` | Boolean flag controlling whether group comparisons are case-sensitive.
Defaults to false (case-insensitive). Only meaningful when
group attribute is specified.
Example: \
| `false` |
| `startRow` | `integer` | `false` | 1-based starting row number for query loops. Only rows from this
position onward will be processed. Must be 1 or greater.
Example: \
| |
| `endRow` | `integer` | `false` | 1-based ending row number for query loops. Processing stops after
this row. Must be 1 or greater and typically greater than startRow.
Example: \
| |
| `label` | `string` | `false` | Optional label for the loop, used with break and continue statements
to control nested loop execution. Allows targeting specific loops
in complex nested structures.
Example: \...\
| |
| `times` | `integer` | `false` | Number of iterations to perform. Creates a simple counting loop
from 1 to the specified number. Can be used with item
or index to access the current iteration number.
Example: \
| |
## Examples
### For Loop (Script Syntax)
General Purpose Loop
[Run Example](https://try.boxlang.io/?code=eJxLyy%2FSUMhUsFUwtAZSNkDaAMjQ1lbQVKjm4iwvyixJ9S8tKSgtAanStOaq5QIARYkNGA%3D%3D)
```java
for( i = 1; i <= 10; i++ ) {
writeOutput( i );
}
```
Result: 12345678910
### For Loop using Bx:loop Tag
General Purpose Loop
```java
#i#
```
Result: 1 2 3 4 5 6 7 8 9 10
### Loop Over an Array (Script Syntax)
Array Loop
[Run Example](https://try.boxlang.io/?code=eJxlkMGqwjAQRdfmKy5dSEul2uVTK6goCML7AHER64gBk0hI0SL%2Bu5Pap09cZEImN%2BcM0fXUOVmjwAaiE8mox3XX1DIS25Ho97G0Dmtrz5jVUGZPVxy4M1%2F%2BZINsAGn2ONkLOcHdGIpR%2BYi3cQEZ0GsyMXSrSfgmTZHgJjoXpzz9Vv5c%2BVdgww%2B3nBL3IGZfcK9MK8vTp6OsnCPjV80syrzpX9iP5D9sM9lClsc4gSa9I4dDZUqvbHDlLGqZGYUQYkxNDTqRZlqvOTx%2FIkEx%2BbK2OXQRYcir%2BxfmAUJ5AJJxb5I%3D)
```java
myArray = [
"a",
"b",
"c"
];
// For Loop By index
for( i = 1; i <= arrayLen( myArray ); i++ ) {
writeOutput( myArray[ i ] );
}
// By For
for( currentIndex in myArray ) {
writeOutput( currentIndex );
}
// By arrayEach()
myArray.each( ( Any element, Any index ) => {
writeOutput( element & " : " & index );
} );
```
### Bx:loop over an Array
Array Loop
```java
#myArray[ i ]#
#currentIndex#
#currentItem#
```
### Loop over a Struct (Script Syntax)
Struct Loop
[Run Example](https://try.boxlang.io/?code=eJx1jk0LgkAQhs%2FOrxh2LwqS9%2FwAA7tEddBbdBDbaFHX2HaLRfzv6ZJkhy7DzPC8H63JldSVwhh7BOeQ7jNcIyk6YYgPTl6khX1sm07yS0lgCCEIcGPwYXVw7aSLlZaSCbVjBrnAdvb0sAfnJbliR63uWrlIooYn9IvT0ZvO%2FGnpc6ZRMLIEvRCGn8isrG6uB7NqxaYbXUyFwZoZ3y7PstFsLBAnfzrUn3ALLrOm8QYmylXE)
```java
myStruct = {
NAME : "Tony",
STATE : "Florida"
};
// By struct
for( currentKey in myStruct ) {
writeOutput( "#currentKey# : #myStruct[ currentKey ]#" );
}
// By structEach()
myStruct.each( ( Any key, Any value ) => {
writeOutput( "#key# : #value#" );
} );
```
### Bx:loop over a Struct
Loop over a Struct using the collection and item arguments of bx:loop.
```java
#currentKey# : #myStruct[ currentKey ]#
```
### Bx:loop over a Struct
Loop over a Struct using the collection, index and item arguments of bx:loop.
```java
#currentKey# : #currentItem#
```
### Loop over a List (Script Syntax)
List Loop
```java
// Define our list
myList = "a, b, c";
// By array
for( item in listToArray( myList, "," ) ) {
writeOutput( item );
}
// By listEach()
myList.each( ( Any element, Any index ) => {
writeOutput( element & " : " & index );
}, "," );
```
### Bx:loop over a List
List Loop
```java
#item#
#currentIndex#
```
### Loop over a Query with Grouping (Script Syntax)
Query Loop use grouping
```java
q = queryNew( "pk,fk,data", "integer,integer,varchar", [
[
1,
10,
"aa"
],
[
2,
20,
"bb"
],
[
3,
20,
"cc"
],
[
4,
30,
"dd"
],
[
5,
30,
"ee"
],
[
6,
30,
"ff"
]
] );
bx:loop query=q group="fk" {
writeOutput( "#fk#
" );
bx:loop {
writeOutput( " #pk#:#data#
" );
}
writeOutput( "
" );
}
```
### Bx:loop over a Query
Query Loop
```java
#myQuery[ "platform" ][ i ]#
#platform#
```
### While Loop (Script Syntax)
Pre-Condition Loop This form of loop evaluates a single condition at the beginning of each iteration, and continues to loop whilst the condition is true
```java
while (condition) {
// statements
}
```
### Do While Loop (Script Syntax)
Post-Condition Loop This form of loop evaluates a single condition at the beginning of each iteration, and continues to loop whilst the condition is true
```java
do {
// statements
}
while (condition);
```
---
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