The ECMAScript 2015 specification introduced a Map class. A Map instance provides convenient methods around key-value-pairs. Objects in JavaScript are key-value-pairs as well. Yet, you can’t pass an existing object to the map constructor. This tutorial shows you how to create a JavaScript map from an existing object. {{outline} …

In a recent project, we needed to calculate differences between data points. Each data point represented an amount of money. The difference between the two data points should always be a positive number in context with prices going up or down. This tutorial shows you how to always retrieve a …

Sometimes you want to pick a random item from a JavaScript array. For example, when picking a winner from a list of participants. Or when highlighting one of your product’s great features. This tutorial shows you how to grab a random array item in JavaScript. {{outline}} Get a Random …

Leaving a loop early is a common practice in programming. Stopping or breaking out of an Array#forEach iteration in JavaScript is only possible by throwing an exception. Also, the Mozilla Developer Network states “when you need to stop forEach, it’s the wrong tool.” This tutorial points you to …

UNIX-based operating systems have a touch utility available on the command line. touch updates the access and modification times of a given file to the current time. A nice benefit: touch also creates the given file if it doesn’t exist. This tutorial shows you how to implement a touch-like …

Creating applications sometimes require you to store a state for a specific user. For example, when working with a command-line application, like npm, you only want to sign in once and NPM should remember your personal access token. Storing a personal access token for a CLI should happen in your …

JavaScript introduced the for…of loops with ECMAScript 2015. The for loop provides a convenient way of iterating over a collection of items. A downside of a for…of loop: by default, it doesn’t give you the item’s index. Yet, you can conveniently work around this shortcoming and …

When interacting with the local hard disk, you may need to check whether an existing path is a file or a directory. Node.js comes with the fs core module providing dozens of useful low-level methods to interact with the hard disk. This tutorial shows you how to compose an …