What do two vertical lines in an object value mean in javascript?
javascript, operators
Solution
This is an `OR` operator. What you need to understand is:
Non-boolean values are converted to a boolean when used in a logic operator. Values that convert to `false` are called "falsy" and values that convert to `true` are called "truthy". Falsy values include things like `0`, `undefined`, `null`, and so on. See more at Truthy and Falsy: When All is Not Equal in JavaScript.
The `OR` operator short-circuits: it keeps evaluating expressions until it finds on that is `true`, and then stops.
So, `var time = $(el).data('start') || new Date();` means "set `time` to the `start` data of the `el` element, OR, if that's falsy, use the current time".
Problem
Possible Duplicate: What does the || operator do? Maybe somebody can provide a better code snippet, but what does `||` mean in the following?: ``` var time = $(el).data('start') || new Date(); ``` Is it an `or` operator and if so, how does it make sense that a variable can have two different values?