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I need to set unit's exhaust.

A unit might have a turnScript, and the turnScript might have a delay. If so, unit.exhaust = unit.turnScript.delay. Otherwise, unit.exhaust = -1.

This is what I have now. It works, but it's repetitive and unidiomatic.

unit.exhaust = unit.turnScript && unit.turnScript.delay ? unit.turnScript.delay : -1;

I tried these two as well:

unit.exhaust = unit.turnScript ? unit.turnScript.delay : -1 || -1;

and

unit.exhaust = {unit.turnScript ? unit.turnScript.delay : -1} || -1;

But the first returns undefined when turnScript exists but not delay, and the second gives me a syntax error (unexpected .). Is there a better way to do it?

share|improve this question
    
:( I was hoping there would be a more succinct way to say it, it's really long. –  Devon Parsons Jun 7 at 20:59
    
Not a ternary, but you could make a function that you'd pass the base object and the two property names to and the function would return the desired result. –  jfriend00 Jun 7 at 21:00
    
Nah, it wouldn't make sense. Pretty much all the units stats are calculated differently, it wouldn't get reused. Thanks though. –  Devon Parsons Jun 7 at 21:00
    
(Note: @jfriend00's comment is now slightly out-of-date. The 'second one' when he commented is the third one as of this comment -- unit.exhaust = {unit.turnScript ? unit.turnScript.delay : -1} || -1;) –  QPaysTaxes Jun 7 at 22:57

1 Answer 1

up vote 3 down vote accepted

You can use short-circuit logic for the whole thing (a ternary is unnecessary). Consider the tree cases:

unit = {}
unit = {turnScript: {}}
unit = {turnScript: {delay: 5}

the results for the output should be:

-1
-1
5

Simple fall-through logic operators will do it:

unit.exhaust = unit.turnScript && unit.turnScript.delay || -1;

as a snippet, this is:

function truthtable(unit) {
  return unit.turnScript && unit.turnScript.delay || -1;
}

var dataNTS = {},
    dataTS = {turnScript: {}},
    dataDel = {turnScript: {delay: 5}};

var out = document.getElementById("output");

out.innerHTML += truthtable(dataNTS) + "\n";
out.innerHTML += truthtable(dataTS) + "\n";
out.innerHTML += truthtable(dataDel) + "\n";
<pre id="output"></pre>

The above function consists of:

  unit.turnScript && unit.turnScript.delay || -1;

It covers the basic use cases and falls through when it has a good answer. The three cases are given as example inputs.

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