Why does “,,,” == Array(4) in Javascript?

Question

Boot up your interpreter/console and try the comparison

> \",,,\" == Array(4)
True

Why? At first I thought maybe since you could think

Answer 1

Try using ===. When using == in Javascript, it will attempt to cast the variables, thus leading to issues like this one. The console is casting Array(4) to the string representation (i.e. Array(4).toString), which is ",,,". The reason the commas are there is that the .toString() function adds them to separate items in an array.

See the snippet below:

document.write( Array(4).toString() );