JSLint and its less opinionated cousin JSHint generate a bunch of warnings. At times these helpers reveal actual issues so you had better take their advice to the heart. I like to use JSHint as it doesn't complain too much but when it's not for nothing. There are plugins available for many editors. It is possible to use the tools as standalone (as a part of your build even).
If you value your time take advantage of these sort of tools. Given JavaScript is so very loose by definition these tools make it a bit less possible to abuse it. You will still run into issues at times but at least these allow you to eliminate some of the most foolish ones. Don't be a fool, use a proper tool.