JSLint is a JavaScript code validator which will check the syntax of the code you have written. Now more often that not when I write my code I leave a comma in where its not needed or miss a bracket which is usually fine in Firefox. But when you try the code in Internet Explorer it throws a wobbly. If I find I am having issues with IE then I put my code through JSLink which highlights any issues with your code. When you have over 100 lines of JS and you know you are hunting down one comma this can be tricky – but this site takes the guess work out of the process.