A few Postman tips for developers

Compute a SHA256 hash, then encode it as base64 string

var base64 = CryptoJS.SHA256("test").toString(CryptoJS.enc.Base64);
console.log(base64);

Save a response as collection variable

var json = JSON.parse(responseBody);
pm.collectionVariables.set("SomeProp", json.SomeProp);

Create a GUID in the pre request script

var uuid = require('uuid');
var guid = uuid.v4();

Generate random string of some length

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.collectionVariables.set("randomString", randomString());