Which Characters Are Allowed in JavaScript Variable Names?

In JavaScript, a variable name:

• Can begin with a letter, underscore (_) or dollar sign ($);
• Can only contain letters, numbers, underscores, or dollar signs;
• Cannot be the same as a JavaScript reserved word;
• Cannot contain spaces;
• Is case-sensitive.

For example, the following are all valid variable names:

const foo = 'bar';
const $foo = 'bar';
const _foo = 'bar';
const _123foo = 'bar';
const foo_bar123$ = 'bar';
const fooBar = 'bar';