Question

Using ternary operator requires two calls to the function.

var colour = (tryAdventurousColour() != null) ? tryAdventurousColour() : 'black';

Possible to do it in 1 line?

EDIT: Fixed syntax
EDIT: Like this but better

var colour = ( (colour = tryAdventurousColour() ) != null ) ? colour : ‘black’;

Answer 1

Use JavaScript’s logical or operator:

var colour = tryAdventurousColour() || 'black';

Your function tryAdventurousColour() will be executed once. If it returns a “truthy” value then that colour variable will be assigned to that value, otherwise colour will be ‘black’. This fits your scenario perfectly since null is a “falsy” value.

In more general terms, the expression a || b returns a if it can be converted to true (is “truthy”), otherwise it returns b. Note that non-zero numbers, non-empty strings and objects will all be converted to true. null, undefined, 0, “” will all be converted to false. (I’m sure somebody will correct me if I’ve left something out.)