How is the data retrieved?

This data is scraped from Indeed. The area you choose is within a 25KM radius and goes through 30 pages of Job postings (400+ Jobs).

How accurate is this?

The accuracy is quite high. The reason for this is each job posting is analysed thoroughly. The only issue is some job postings do list multiple programming languages/technologies so it can't always be completely accurate.

If a technology is the highest on the chart, this means it was the most mentioned across all job postings in your area.

Why is JavaScript extremely popular?

Web Development has become very popular over last decade and JavaScript has evolved over this period. Due to this, developers that know JavaScript is a usually a huge plus. This doesn't mean that JavaScript is the be all and end all though. There are plenty of areas where different technologies are used.