Javascript quick reference

2020-01-10

Variable	`typeof x !== 'undefined'`	`x != null`	`x!== null`	`x ? true : false`
`let varOne = 1;`	`true`	`true`	`true`	`true`
`let varEmpty = 0;` (or empty string / structure)	`true`	`true`	`true`	`false`
`let varNull = null;`	`true`	`false`	`false`	`false`
`let varUnDefined;`	`false`	`false`	`true`	`false`
Variable is undeclared	`false`	exception	exception	exception

Returning from function without value returns undefined.

const object can be changed, but cannot be reassigned to point to another object.