A list of my reusable functions that I use in Postman's Package Library feature.

utils.js

/**
 * Create a random string length between the speficied min / max values
 * @param {Number} minValue - The min value of the string length
 * @param {Number} maxValue - The max value of the string length
 */
const randomString = function (minValue, maxValue, dataSet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz') {
    const lodash = require('lodash');
    if (!minValue) {
        minValue = 10;
        maxValue = 10;
    }
    if (!maxValue) {
        maxValue = minValue;
    }
    let length = lodash.random(minValue, maxValue),
        randomText = "";
    for (let i = 0; i < length; i++)
        randomText += dataSet.charAt(Math.floor(Math.random() * dataSet.length));
    return randomText;
}

/**
 * Create a random alphanumeric string between the speficied min / max values
 * @param {number} minValue - The min value of the string length
 * @param {number} maxValue - The max value of the string length
 * @param {string} dataSet - Optional. The base dataset to create the alphanumeric string 
 */
const randomAlpha = function (minValue, maxValue, dataSet = 'abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ') {
    return randomString(minValue, maxValue, dataSet);
}

/**
 * Converts a date string into the format 'DD/MM/YYYY'
 * @param {string} date - The date value to be converted
 */
const formatDate = function (date, format = 'DD/MM/YYYY') {
    let moment = require('moment');
    return moment(date).format(format);
}

/**
 * Converts a Unix Timestamp to the format 'DD/MM/YYYY'
 * @param {number} time - the timestamp in unix format
 */
const convertTimestamp = function (time, format = 'DD/MM/YYYY') {
    let moment = require('moment');
    return moment.unix(time).format(format);
}

/**
 * Checks if a given date is after another date
 * @param {string} baseDate - The base date to check
 * @param {string} comparisonDate - The comparison date to check against
 * @returns {Boolean} Returns true if the date is before the given date
 * @example .isDateBefore("2004-04-04T04:04:04", "2006-04-04T04:04:04")
 */
const isDateBefore = function (baseDate, comparisonDate) {
    let moment = require('moment');
    return moment(baseDate).isBefore(comparisonDate);
}

/**
 * Checks if a given date is after another date
 * @param {string} baseDate - The base date to check
 * @param {string} comparisonDate - The comparison date to check against
 * @returns {Boolean} Returns true if the date is after the given date
 * @example .isDateAfter("2004-04-04T04:04:04", "2006-04-04T04:04:04")
 */
const isDateAfter = function (baseDate, comparisonDate) {
    let moment = require('moment');
    return moment(baseDate).isAfter(comparisonDate);
}

/**
 * Checks if the API response is returned in less than a given value
 * @param {number} ms - Expected response time is milliseconds
 */
const checkResponseTime = (ms) => {
    pm.test(`Response time should be less than ${ms}`, () => {
        pm.expect(pm.response.responseTime).lt(ms);
    });
}

/**
 * Checks if the API response has a given status code
 * @param {number} code - Expected response status code
 * @param {string} message - Optional assertion failure message
 */
const checkStatusCode = (code, message = "Status code does not match") => {
    pm.test(`Status code should be ${code}`, () => {
        pm.expect(pm.response.code, message).to.equal(code);
    });
}

/**
 * Clears the Environment variables which match a specific prefix value
 * @param {string} prefix - The prefix given to a variable that will be cleared after the function is run.
 * @example .cleanupEnvVars("temp_")
 */
const cleanupEnvVars = (prefix) => {
    const lodash = require('lodash');
    const clean = lodash.keys(pm.environment.toObject())
    lodash.each(clean, (arrItem) => {
        if (arrItem.startsWith(`${prefix}`)) {
            pm.environment.unset(arrItem)
        }
    })
}


module.exports = { randomString, randomAlpha, formatDate, convertTimestamp, isDateBefore, isDateAfter, checkResponseTime, checkStatusCode, cleanupEnvVars }