- Tab indentation
- Single-quotes
- Semicolon
- Strict mode
- No trailing whitespace
- Multiple variable statements
- Space after keywords and between arguments and operators
- Return early
- JSHint valid
- Consistency
Example:
'use strict';
function foo(bar, fum) {
    var ret;
    var hello = 'Hello';
    if (!bar) {
        return;
    }
    for (var i = 0; i < bar.length; i++) {
        if (bar[i] === hello) {
            ret += fum(bar[i]);
        }
    }
    return ret;
}Read idiomatic.js for general JavaScript code style best practices.
See
XOfor this code style as a linter.