Update: @twitinsin points out that it’s still useful in the console for quickly declaring multiple variables.
I developed the habit of always using var when I write JavaScript long ago. At some point I got in the habit of typing var even when I’m using a JavaScript console in node or in a browser. After examining the issues I’ve decided to break that habit.
I think I got in the habit of this because I came to appreciate explicit variable declaration, and decided to gladly pay the tax. The four extra characters, including the space, isn’t bad. But it doesn’t serve a useful purpose in short console sessions. Without var, it’s still valid JavaScript, that will run in node.js and in any browser. It won’t pass JSHint and JSLint, which is why it should always be added before delivering code.
If this gets me to be just a little quicker to fire up a REPL (a more generic term which includes the JavaScript console), it will be an improvement.