Learn JavaScript Programming

We first call the function, then we have a then() method that is called when the function ends. As we saw in the previous chapter, with callbacks we’d be passing a function to another function call that would be called when the function has finished processing. You can set the value of a property when you define the object. As you can see, when we have multiple properties, we separate each property with a comma. They are very often used instead of “regular” functions, the ones I described in the previous chapter.

  • Take your JavaScript knowledge to the next level by learning how to use advanced functions to create more efficient programs.
  • I personally prefer single quotes all the time, and use double quotes only in HTML to define attributes.
  • You will write simple JavaScript statements in the web browser console and be able to create variables and arrays.
  • JavaScript is also now widely used outside of the browser.

Instead, it’s part of the vast library of APIs provided to us in the browser. Sometimes it’s hard to separate JavaScript from the features of the environment JavaScript Lessons it is used in. Other languages exist, but all must compile to JavaScript – or more recently to WebAssembly, but this is another story.

The easiest way to  learn  &  practice  modern JavaScript

An identifier is a sequence of characters that can be used to identify a variable, a function, or an object. It can start with a letter, the dollar sign $ or an underscore _, and it can contain digits. Using Unicode, a letter can be any allowed character, for example, an emoji ?.

Medium is a blogging platform that gives writers a place to share their thoughts with others. There are a lot of medium publications that publish articles about programming. DEV is a community of software developers writing articles to learn and help one another out.


Some developers will always use semicolons, some others will never use semicolons, and you’ll always find code that uses semicolons and code that does not. In JavaScript, we can write a comment on a single line using //. Everything after // is not considered as code by the JavaScript interpreter.

JavaScript Lessons


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