A very easy rule of thumb where semicolons are necessary and allows you not to add semicolons at the end of all statements:

• In for loops: for(var i = 0; i < 10; i++){}
• In a body-less loop: while(i === 0);
• If a line starts with any of these characters:
  • ( example ;(function(){})()
  • [
  • +
  • -

You anyway have to add these semicolons because when your files will get concatenated/minified these statements may be right after a library that doesn’t use semicolons.

Never break lines for

There are only few cases where line-breaking does not concatenate statements (applies to both semicolon-everything and semicolon-less approach):

• return
• break
• continue
• throw