Main goals

Be consistent, but not religious about the style.
Use tools to keep aligned with the guidelines.
Strive for readable code and simple expressions.
Eliminate all inconsistencies you spot.
Strive for Functional Programming style.

Whitespaces

Space indentation for all files (2 spaces). See .editorconfig
Smart tabs are ok.
Use one space after if, for, while, etc.
Use one space after function for anonymous functions but not for named functions:

var fn = function () {}
function fn() {}

Don't leave trailing whitespace at the end of lines.

Variables

Use one var per variable unless you don't assign any values to it (and it's short enough):

var smth = 123
var next, prev, idx

Use lowerCamelCase for variables and properties.
User UPPERCASE for constants.

Comments

Comment all non-obvious stuff.

Functions

Use named functions. They make stack traces a lot easier to read.
Avoid anonymous functions in chains.
Use lowerCamelCase for function and method names.
User UpperCamelCase for class names.

General style requirements

1TBS
Single quotes for strings, unless you are writing JSON.
Leading dot for chain calls.
use strict;
Use === operator.
Write small functions (no more than 15 expressions).
Avoid deeply nested expressions (max depth = 3).
All projects must have pre-commit hooks for linting (use husky).
Use .jshintrc and .editorconfig

In case of emergency

Inspired by