What Are the Most Popular JavaScript Keywords? and What This Means for ECMAScript 6

Ariya Hidayat has used his Esprima parser to count the most popular keywords in a corpus of JavaScript libraries.

The five most popular ones are (by far):

• 19.2%: this
• 18.5%: function
• 18.2%: if
• 17.1%: return
• 12.6%: var

Quoting a comment by Thomas Fuchs:

As an interesting aside, CoffeeScript eliminates two out of the first five completely (return and var), and has much shorter ways to express function (->) and this (@).

Functional-programming-style implicit return of the last value in a block is indeed a good idea and will probably make it into ECMAScript 6 in one form or another. One should not forget that the brain recognizes tokens, not characters, which means that for reading code (which is much more important than writing code), shorter tokens don’t matter much. That being said, a shorter function notation will probably also be part of ECMAScript 6 and is appreciated. I do like that JavaScript has a keyword for declaring variables (var now, let soon), because that helps with checking for typos.

For more information, including a diagram of the distribution of the keywords, consult Ariya Hidayat’s article.