Generate Random String in Postman

Question

I'm new at postman an im trying to generate a random string with letters(A-Z) and numbers(0-9). The string should have 20 points. I don't know how to set the Body and the pre req. I know that the Request must be POST. I have no idea how to start.

Answer 1

You can add scripts to the Pre-request Script to create this value.

This function will create the random value from the characters in the dataset and it will be 20 characters in length - The length can be adjusted when calling the function with your desired min and max values.

function randomString(minValue, maxValue, dataSet = 'abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ') {
    if (!minValue) {
        minValue = 20;
        maxValue = 20;
    }

    if (!maxValue) {
        maxValue = minValue;
    }

    let length = _.random(minValue, maxValue),
        randomString = "";

    for (let i = 0; i < length; i++)
        randomString += dataSet.charAt(Math.floor(Math.random() * dataSet.length));
    return randomString;
}

pm.variables.set('randomString', randomString());

Adding a basic body like this is how you can use the randomly generated value:

{
    "randomValue": "{{randomString}}"
}

When the request is sent, it will execute the function in the Pre-request Scripts tab and set the value as a local variable, this will then be used in the body of the request:

Answer 2

Per postman's docs you should be able to use {{$randomAlphaNumeric}} to generate a single character. $randomPassword seems to just generate 15 random alpha numeric characters so something like:

{{$randomPassword}}{{$randomAlphaNumeric}}{{$randomAlphaNumeric}}{{$randomAlphaNumeric}}{{$randomAlphaNumeric}}{{$randomAlphaNumeric}}

should give you 20 random characters without writing much code. This is a little terse, you could also just use the $randomAlphaNumberic selector 20 times.