Create a count-based loop with the Repeat block

You can build a flow that loops over a count. For example, you can run a flow that loops over a count of three and generates a list of three random numbers.

This tutorial's goal is to teach you how to set up and use count-based loops. To achieve this goal, you'll build a flow that uses a loop to count to three.

Create a new flow

You build flows in a workspace. Workspaces let you organize your API projects and collaborate with your team.

To create a new flow, do the following:

1. Choose an existing workspace or create a new one.
2. From the Postman sidebar, select Flows.
3. Select Create a new Flow > Create new Flow.
4. Enter a name. For example, enter Create a count-based loop.
5. Select the Return or Enter key.

Add a Repeat block

The Repeat block lets you build a loop that iterates over a count. For example, to run a loop three times, set the count to three.

In the next procedure, you'll use the Number block to define this count.

To add a Repeat block, do the following:

1. From the canvas toolbar, select Block.
2. Select Repeat. If you want to search for the block, enter Repeat in search.
3. Decide where on the canvas you want to place the Repeat block and select that location.

Connect a Number block

When you connect two blocks, you connect one block's input to another block's output. Inputs are on the block's left side and outputs are on its right side.

In this tutorial, you'll use the Number block to define the number of times you want to run your loop.

To connect a Number block, do the following:

1. Hover over the Repeat block's Count input port. The pointer changes to a crosshair.
2. Decide where on the canvas you want to place the Number block and drag the port to that location.
3. Select Number. If you want to search for the block, enter Number in search.
4. Enter a whole number. For example, if you want your loop to repeat three times, enter 3.

Connect an Evaluate block

Many programming languages start counting with an index value of zero (for example, 0, 1, 2).

In the following steps, you'll use an Evaluate block to add one to the count to start counting with an index value of one (for example, 1, 2, 3).

To connect an Evaluate block, do the following:

1. Hover over the Repeat block's output port. The pointer changes to a crosshair.

2. Decide where on the canvas you want to place the Evaluate block and drag the port to that location.

3. Select Evaluate. If you want to search for the block, enter Evaluate in search.

4. Rename the variable. For example, enter index.

5. Add the following to the code editor:

   index + 1
   

This code takes the index, which starts at zero, and adds one.

Alternatively, use the Flows Query Language (FQL) $now() function to timestamp the loop. This is another great way to conceptualize what happens when you run a loop.

Connect a Collect block

The Collect block saves multiple outputs to a list. In this tutorial, your loop will run three times, output three values, and use this block to save these values to a list.

To connect a Collect block, do the following:

1. Hover over the Evaluate block's output port. The pointer changes to a crosshair.
2. Decide where on the canvas you want to place the Collect block and drag the port to that location.
3. Select Collect. If you want to search for the block, enter Collect in search.

Connect an Output block

The Display block displays incoming data, such as the Collect block's outgoing list.

To connect a Display block, do the following:

1. Hover over the Collect block's output port. The pointer changes to a crosshair.
2. Decide where on the canvas you want to place the Output block and drag the port to that location.
3. Select Output. If you want to search for the block, enter Output in search.

Run the flow

From the canvas toolbar, select Run.

Congratulations! You created a count-based loop and displayed the result in a Display block.