README.FIRST This write-up is a log of the author’s personal challenge to learn the bare minimum basics of in a tight timeline for a specific purpose. JavaScript Please, take this piece as a “foundation building up reading” if you are someone like me who just want to take API testing and the automation of rigorous tasks a step further with Postman and JavaScript. The author logged the bare-minimum JS basics he thinks are needed for API testing scripting in . As such, this article omitted a good number of important topics like and loops and - flow etc. that are a must for those who want to learn JS seriously. Postman forEach while try catch The target audience of this log is SQA engineers and testers who have prior knowledge of one or two programming languages and clearly know what they are doing to get what output. Scripting Scopes in Postman: Pre-request Script and Tests Just a humble revision to the scripting scopes in is given below: Postman : In this tab, we write the scripts that will be run before making an HTTP request. These scripts include setting up and assigning environment variables, any modification of the request body, etc. Pre-request Script : Scripts written in this tab are run after an HTTP request ends. These scripts include different tests like looking for specific data in the response body, setting up environment variables for the next request/s, testing response codes and time, etc. Tests : Response body is shown in this window. We can select format options like , etc. from there. Response JSON HTML : This tab prints the request headers, errors, and any JavaScript code outputs. Console You need not to worry about running the collection. . It is available in the cloud here For this tutorial, I used test APIs in . DummyJSON Postman has a runtime that gives us the ability to modify HTTP requests dynamically. node.js The scripts we write in the Pre-request and Tests tabs are run in the Postman sandbox. The following resources are two must bookmarks for an  API tester who uses Postman Scripting in Postman Postman JavaScript reference Day 1: Variables Variables are the fundamental building blocks of a program or script. We store values in them. A variable in JavaScript can be declared using either , or keywords. var let const As I have a specific scope for writing test cases for ,  I have chosen and for brevity after doing some R&D with a JS veteran and on the internet. Postman let const Using for variables that can be changed dynamically let let x = "ASDF"; 
console.log(x);
x = [1,2,3];
console.log(x); Using for variables that should be untouched const const lifeOfGeek = {
    first: "Family",
    second: "Geeky Things",
    third: "Career"
}; 

// avoid an accidental assignment in the same scope
lifeOfGeek = {
    first: "Greed",
    second: "Drugs",
    third: "Polygamy"
};
/*
$ node lifeOfGeek.js 
{ first: 'Family', second: 'Geeky Things', third: 'Career' }
life = {
     ^
TypeError: Assignment to constant variable.
...
*/ In the following example, we will declare some JS variables, set and get environment variables in the and tabs that are the fundamental building blocks to script in the tool. Postman Pre-request Script Tests API testing Example Request: DAY_1_All_Products_VARIABLES Action : Submit The following codes are self-explanatory: tab Pre-request Script // Set an environment variable without any initial value 
pm.environment.set("eighthProduct");

// Set an environment variable with an initial value 
pm.environment.set("PI", 3.141); tab Tests // Assign response data in a JSON object
let jsonData = pm.response.json();

// Assign the 6th object to sixthProduct
let sixthProduct = jsonData["products"][5]; 
console.log("sixthProduct: ", sixthProduct);

// Assigning value to a pre-request script environment variable 
pm.environment.set("eighthProduct", jsonData["products"][7]);
console.log("eighthProduct: ", pm.environment.get("eighthProduct"));
console.log("PI: ", pm.environment.get("PI")); Sample response {
    "products": [
        {
            "id": 1,
            "title": "iPhone 9",
            "description": "An apple mobile which is nothing like apple",
            "price": 549,
            "discountPercentage": 12.96,
            "rating": 4.69,
            "stock": 94,
            "brand": "Apple",
            "category": "smartphones",
            "thumbnail": "https://i.dummyjson.com/data/products/1/thumbnail.jpg",
            "images": [
                "https://i.dummyjson.com/data/products/1/1.jpg",
                "https://i.dummyjson.com/data/products/1/2.jpg",
                "https://i.dummyjson.com/data/products/1/3.jpg",
                "https://i.dummyjson.com/data/products/1/4.jpg",
                "https://i.dummyjson.com/data/products/1/thumbnail.jpg"
            ]
        },
... Please read the section in my GitHub repository to learn more about Day 1 7_Days_of_JS JavaScript variables. Day 2: Arrays Arrays are indexed collections of the same or different types of objects. The behavior of arrays varies on the philosophy of programming languages. A JavaScript array can hold multiple types of objects in its indexes. The basics of JS arrays are available in my GitHub repository. The examples are well commented. here In the following script, we will extract an array from a JSON response and append some arbitrary data in it. Tests : Example Request Day_2_All_Products_ARRAYS : Action Send Now look at the response JSON in the tab of the response window. We will extract the array of the sixth item from it, which  holds different images of a . Body images MacBook Pro ...
{
            "id": 6,
            "title": "MacBook Pro",
            "description": "MacBook Pro 2021 with mini-LED display may launch between September, November",
            "price": 1749,
            "discountPercentage": 11.02,
            "rating": 4.57,
            "stock": 83,
            "brand": "Apple",
            "category": "laptops",
            "thumbnail": "https://i.dummyjson.com/data/products/6/thumbnail.png",
            "images": [
                "https://i.dummyjson.com/data/products/6/1.png",
                "https://i.dummyjson.com/data/products/6/2.jpg",
                "https://i.dummyjson.com/data/products/6/3.png",
                "https://i.dummyjson.com/data/products/6/4.jpg"
            ]
        }, 
... Let’s parse the JSON, extract and print the expected array in the console let jsonData = pm.response.json();
let sixthElementImages = jsonData.products[5]["images"];
/*
The above statement is equivalent to the following-
let sixthElementImages = jsonData["products"][5]["images"];
*/
console.log("sixthElementImages values: ", sixthElementImages);
/*
Expected Output 
"sixthElementImages values: "
> (4) ["https://i.dummyjson.com/data/products/6/1.png", "https://i.dummyjson.com/data/products/6/2.jpg", "https://i.dummyjson.com/data/products/6/3.png", "https://i.dummyjson.com/data/products/6/4.jpg"]
*/ Click the small arrow sign beside to expand the object for a more readable formatted view. (4) The array contains four URLs to a laptop. MacBook Pro Now, we will different types of objects into it and see the effect. push sixthElementImages.push("A Quick Brown Fox");
sixthElementImages.push(["https://discord.com/", "https://www.notion.so/"]);
sixthElementImages.push(3.1141);

console.log("After push sixthElementImages values: ", sixthElementImages);
/*
Expected Output
"After push sixthElementImages values: " 
> (7) ["https://i.dummyjson.com/data/products/6/1.png", "https://i.dummyjson.com/data/products/6/2.jpg", "https://i.dummyjson.com/data/products/6/3.png", "https://i.dummyjson.com/data/products/6/4.jpg", "A Quick Brown Fox", …]
	0: "https://i.dummyjson.com/data/products/6/1.png"
	1: "https://i.dummyjson.com/data/products/6/2.jpg"
	2: "https://i.dummyjson.com/data/products/6/3.png"
	3: "https://i.dummyjson.com/data/products/6/4.jpg"
	4: "A Quick Brown Fox"
	5: [2]
		0: "https://discord.com/"
		1: "https://www.notion.so/"
	6: 3.1141
	*/ Notice, the length of is increased from to as we pushed three new objects into it. Basic indexed operations are similar to other programming languages. sixthElementImages 4 7 An interesting twist for geeks—  a JS array is an object under-the-hood. PoC console.log(typeof sixthElementImages); Day 3: Objects Objects, a pair entity, play a vital role in JavaScript language that is used to store different types of data, variables, and functions for using them efficiently. In JavaScript, we can directly declare objects without creating a class. key:value Let’s declare a simple object. const pcConfig = { // ... 1
	cpu: 'intel i5', 
	cores: 4,
	ram: '16 GB',
	motherBoard: 'Asus',
	'operating-system': {  // ... 2
		name: 'Debian',
		version: 11, 
		bits: 64
	}  
}; Some features of an object to be noticed: It is a common practice to declare an object with for avoiding unexpected assignments. This will be elaborated on later. const Although names can be written without quotations, it is mandatory to use them if the key contains any special character or words reserved for JS. key/property Here is a PoC why we use for declaring an object const const pcConfig = { // ... 1
	cpu: 'intel i5', 
	cores: 4,
	ram: '16 GB',
	motherBoard: 'Asus',
	'operating-system': {  // ... 2
		name: 'Debian',
		version: 11, 
		bits: 64
	}  
};

pcConfig["rgbLight"] = "N/A"; 

console.log(pcConfig);

pcConfig = "ASDF"; // avoid accidental reassignment

/*
$ node objectTest.js # Expected output 
{
  cpu: 'intel i5',
  cores: 4,
  ram: '16 GB',
  motherBoard: 'Asus',
  'operating-system': { name: 'Debian', version: 11, bits: 64 },
  rgbLight: 'N/A'
}
pcConfig = "ASDF"; 
         ^
TypeError: Assignment to constant variable.
...
*/ There are two more important fundamental concepts of and copy of JavaScript objects discussed in my . The code is self-explanatory with necessary comments. deep shallow GitHub repository In the following example, we will convert a JS object into a JSON object and send the request body in a method to create an entity in the remote server. POST // Declare a JS object
const jsObject = {
  id: 1000,
  title: 'Linux Phone 10',
  description: 'Custom Linux OS on custom embeded system',
  price: 1000,
  discountPercentage: 50,
  rating: 4.99,
  stock: 150,
  brand: 'Not Applicable',
  category: 'smartphones',
  thumbnail: 'https://linuxstans.com/wp-content/uploads/2022/02/volla-phone@2x.jpeg'
};
// The type is object
console.log(typeof jsObject);

// Convert the object into a string
let jsonData = JSON.stringify(jsObject);
// Notice: They keys or properties are now in double quotes
console.log(jsonData);

// The type is string
console.log(typeof jsonData); Note: Keep in mind that JSON and JS objects are two different things. Now paste this string into the request body, select radio button and select from the right drop-down menu and finally, click the button to make the string more readable. POST raw JSON Beautify Example Request: Day_3_POST_Add_Product_OBJECTS Action: Submit JSON in tab after beautification Body {
    "id": 1000,
    "title": "Linux Phone 10",
    "description": "Custom Linux OS on custom embeded system",
    "price": 1000,
    "discountPercentage": 50,
    "rating": 4.99,
    "stock": 150,
    "brand": "Not Applicable",
    "category": "smartphones",
    "thumbnail": "https://linuxstans.com/wp-content/uploads/2022/02/volla-phone@2x.jpeg"
} Day 4: Loops A loop repeats the workflow of a code block for a limited or infinite time. There are four types of loops in JavaScript for Conventional .. loop for in .. loop for of loop that calls a callback function to control the workflow forEach I will discuss and in a  future article. forEach while The syntax of the first three type of loops are: for // Conventional
for(let i = 0; i < lengthOfArray; i++){
    //codes here
}
// for .. in
for(index in object){
    //codes here
}

// for .. of
for(object of objectCollection){
    //codes here
} A rule of thumb to remember the .. vs .. is for in for of an of .. returns the index of an object in for in an of .. returns the value or object of a collection of objects of for of Day 5: Flow The basic execution flow of a JavaScript code is controlled by blocks. if else The following code chunk written in the block filters outs odd-number product ids that are divisible by and Tests 15 23 : Example Request Day_5_All_Products_FLOW : Action Send let jsonData = pm.response.json();
let productsArray = jsonData["products"];

for(element of productsArray){
    // Filer the odd ids that are divisable by 15
    if(element["id"] % 2 !== 0 && element["id"] % 15 === 0){
        console.log(element)
    }

    // Filer the odd ids that are divisable by 23
    else if(element["id"] % 2 !== 0 && element["id"] % 23 === 0){
        console.log(element)
    }
}

/*
Sample Output 
{id: 15, title: "Eau De Perfume Spray", description: "Genuine  Al-Rehab spray perfume from UAE/Saudi Arabia/Yemen High Quality"…}
 
{id: 23, title: "Orange Essence Food Flavou", description: "Specifications of Orange Essence Food Flavour For Cakes and Baking Food Item"…}
 
{id: 45, title: "Malai Maxi Dress", description: "Ready to wear, Unique design according to modern standard fashion, Best fitting ,Imported stuff"…}
 
{id: 69, title: "Golden Watch Pearls Bracelet Watch", description: "Product details of Golden Watch Pearls Bracelet Watch For Girls - Golden Chain Ladies Bracelate Watch for Women"…}
 
{id: 75, title: "Seven Pocket Women Bag", description: "Seven Pocket Women Bag Handbags Lady Shoulder Crossbody Bag Female Purse Seven Pocket Bag"…}

*/ I will discuss and in a future article. try catch Day 6: Functions A function is a group of codes that we can reuse in a scope. This is the very first concept of code re-usability. The format of a function in JavaScript is given below function functionName(param1, param2, ...){
	// Codes here 
	return returnValue1, returnValue1, ... ;
}

// Calling a function
functionName(param1, param2, ...); Let’s write a basic function in the tab that will check if an input is a prime number or not. Tests function isPrime (number) {
	let prime = true;
	if (number === 1 || number === 0) {
		return prime = false;
	}

	for (let i = 2; i < number; i++) {
		if (number % i === 0) {
			return prime = false;
		}
	}
	return prime;
} Now, we will use this code block in a Postman request to filter out products that have a prime number price value. : Example Request Day_6_All_Products_FUNCTIONS : Action Send let jsonData = pm.response.json();
let productsArray = jsonData["products"];
console.log("Products that have prime no. price values")
for(element of productsArray){
    // Filter prices that are prime in vlaues
    if(isPrime(element["price"])){
        console.log(element);
    }
}

/*
// A truncated view of the output in the Console

> {id: 69, title: "Golden Watch Pearls Bracelet Watch", description: "Product details of Golden Watch Pearls Bracelet Watch For Girls - Golden Chain Ladies Bracelate Watch for Women"…}
...
id: 69
title: "Golden Watch Pearls Bracelet Watch"
description: "Product details of Golden Watch Pearls Bracelet Watch For Girls - Golden Chain Ladies Bracelate Watch for Women"
price: 47
...
*/ Wrapping it Up So far this was my 7-day journey to explore the tip of the JavaScript iceberg. In the next installment, I will come back with the basics of how to write test cases in Postman using JavaScript along with other necessary API testing tips and tricks. I also wish to make Bangla video tutorials on API testing with JS and Postman in the future. Until then, ! Happy Hacking

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