while component: Conditional loop node. It executes the target node or rule chain repeatedly as long as the specified condition is met.

Configuration

Field	Type	Description	Default
condition	string	The loop condition expression using el expression language. E.g., msg.count==nil \|\| msg.count < 5.
do	string	The Node ID or Sub-Rule Chain ID to execute in each iteration.
mode	int	How to handle output after the loop finishes. 0 - Ignore, 1 - Append/Merge, 2 - Override	0

mode

• 0(Ignore) - Outputs the original message as it was before the loop started.
• 1(Append) - Merges the msg.Data produced in each iteration into a JSON array as the final output, preserving the metadata from the last iteration.
• 2(Override) - Uses the exact result (Data and Metadata) of the last iteration directly as the output.

TIP

Difference from the For node: In a While node, the result of each iteration (including modified metadata) must be passed as input to the next iteration. This ensures the condition can change dynamically to prevent infinite loops. It acts as a state-continuous conditional loop. In contrast, a For node generally provides an isolated context for each iteration.

Relation Type

• Success: After the loop finishes, the message is passed along the Success chain.
• Failure: If an error occurs during expression evaluation or iteration, the message is passed along the Failure chain.

Execution Result

During the loop, the result of the previous iteration is used as input for the next iteration. When the condition evaluates to false and the loop completes, the final output message depends on the mode:

• mode=0: Outputs the original message as it was before entering the component.
• mode=1: Collects results from each iteration into an array, and outputs the final message replacing msg.Data with this array.
• mode=2: Outputs the final result of the last iteration directly.

Iteration Context Variables

During iteration, the component sets the following metadata variables:

• _loopIndex: Current iteration index (starting from 0).

Breaking the Loop

If the message metadata contains _break with value true during iteration, the loop terminates immediately.

Configuration Example

{
  "id": "s1",
  "type": "while",
  "name": "While Loop",
  "configuration": {
    "condition": "msg.count==nil || msg.count < 5",
    "do": "s2"
  }
}