Voice of a Developer: JavaScript JSLint v2

This is a continuation of the last article on JSLint, we will start with Options and command-line utility of JSLint. Connect the dots where we left now, but read the last article (link) before reading this one otherwise you will feel nausea, drowsiness, and feel unhappy.

Go to URL: http://www.jslint.com/

You can fiddle with JSLint and customize your warnings via Options below:

I am going to show commonly used options here:

Assume=> in development: select this when you are using debugging code, troubleshooting and code includes statements like console, alert, etc.
1. var array = [2,4,16];
2. var output = array.map(Math.sqrt);
3. alert(output);
If ‘in development’ is unchecked, you will get below warning:
Assume=> ES6 checkbox: if you’re using ES6 features in your code and you try it without selecting this checkbox it’ll give you a warning, ex-
1. let array = [2,4,16];
3. var output = array.map(Math.sqrt);
Assume=>a browser: your code is leveraging global variables accessible in browser ex- window, the document then you can click this checkbox and mention these specifically in global variables, refer snapshot below:

Code
1. function f1() {
2. var array = [2,4,16];
3. var output = array.map(Math.sqrt);
4. window.alert(output);
5. }

Function report

It displays an output showing about global objects and objects leveraged inside our function.

What is the biggest problem in JavaScript?

Answer: I am going to share my opinion that it is not possible to determine at compile time if you misspell the name of variables. The risk is it will create global undefined variables. As an outcome, developers will spend a lot of time troubleshooting and debugging code. If front-end code grows exponentially then code smells in absence of right design and best practices.

FYI: Another advantage of JSLint is that it can read JSON also.

Command-line support

As developers, we love command prompt. The good news is JSLint is available as a node module and we will learn how to lint our JS files locally.

Assumption: I believe you have NodeJS installed, if not please refer to my article number 6 of this series. We will first install the jslintJSLint npm package in the existing NodeJS repository.

Steps

Open GIT bash and goto NodeJS repository.
Run below command to install jslint.

npm install jslint -g
Run jslint from the command line to lint your code.

Example lets revistrevisit our script we wrote on JSlint.com and save as ‘script.js’
1. 'use strict';
2. function f1() {
3. var x ={a:1, b:2};
4. alert(x);
5. }
Above Warnings we have seen at web applications are now appearing on the command line. The benefit of the command line is integration with your code and during continuous integration & deployment.
We could pass Options in command-line utility as well, but before that check syntax:
In order to remove above Warnings we could pass on Options as following:

Summary

I believe now you have a good understanding of the linting &JSlintJSLint tool. There are many other tools available in JavaScript like JShintJoshing, ESlintSlant. Some of these were forked from JSlintJSLintgithubGitHub repository and based on JSlintJSLint fundamentals but differ in some contexts.

12 Comments

Join the conversation! Your thoughts help the community grow.

Rajib Das Gupta10y ago
Nice
Bhuvanesh Mohankumar10y ago
Good one
Kuppurasu Nagaraj10y ago
Nice sharing..
Guest User10y ago
I hope it helps... please let me know incase you've any more questions... Thanks for asking
Guest User10y ago
Now JSLint gives you wanring using these is because you need to mention window in Global variables to use functions which are associated with any Global object in parsing.. try at http://www.jslint.com/
Guest User10y ago
In JSLint or JavaScript, there is no difference if you use alert or window.alert...
Guest User10y ago
Dear Manju lata Yadav I am not clear on your question? Can you please elaborate?
- Manju lata Yadav10y ago
  Actually Sumit, I want to the difference betwen alert() and window.alert() for JSLint,
Manju lata Yadav10y ago
Why it shows undeclared alert when we do not choose in development as both alert and window.alert() are same.
Guest User10y ago
thnx! good day'
Sonu Chaudhary10y ago
good one...
Debasis Saha10y ago
Nice One..

Voice of a Developer: JavaScript JSLint v2 - Part 23

Introduction

Function report

What is the biggest problem in JavaScript?

Command-line support

Summary