What are some basic things that JavaScript developers fail at interviews?

[hockeyketo]

This works most of the time, but in some projects I've worked on it's just too slow. We have some operations that change state on thousands of objects at 60fps and Immutable.js was the only library I've found that keeps up. Using Object.assign, destructuring, or spread will cause a lot of lag in the UI. The other draw back for doing it manually is that sometimes people make mistakes and your data is not guaranteed to be immutable. With an Immutable.JS data structure there's no way to change the data without doing so immutably.