Personalization Glossary

Synchronous JavaScript

Whenever a web page tries to load, your browser looks for directions within the site’s code, which almost always include JavaScript tags. The tags control what content is delivered to each visitor and also impact a website’s speed in regard to loading times. JavaScript has two forms, “Synchronous JavaScript” and “Asynchronous JavaScript.” We will describe the first form here, but please read through our “Asynchronous JavaScript” description to better compare the two.

“Synchronous JavaScript” is read by your browser as its name suggests: in a synchronous order. Logically, this may sound great, but in reality, it means slower loading times as the next action can’t begin until the previous action has completed. Slower loading times may cause companies visitor loyalty and revenue gains in a fraction of a second.

The web development community is working on an alternative, “Asynchronous JavaScript,” which can run multiple commands at time without waiting for another to finish, but this has issues yet to be resolved. JavaScript has a specific construct, “document.write,” which requires synchronous loading. This construct is used for inserting various items into a website and is almost always present in JavaScript code.

Alternatives are being worked on in tandem, varying between manufacturer solutions (for example, HTML5) and tag-writing library solutions (tools that convert synchronous scripts into asynchronous scripts). Until an ideal solution is reached, website developers should test their websites’ load times frequently and ensure their performance speeds are maximized to the best of their ability.

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