Javascript – Should the ternary operator be used outside of assignment statements

javascript

Edit This isn't a question of whether or not the ternary operator is harmful. It's about whether or not there's a consensus about whether or not it should be used outside of assignment statements. /Edit

Based on a boolean, I want to call one of two different functions (with no return value). I wrote this bit of javascript:

(condition) ? doThis(arg) : doThat(arg)

Which I think looks cleaner than writing out an if-else statement:

if(condition) {
    doThis(arg);
}
else {
    doThat(arg);
}

My colleagues strongly believe ternary statements should only be used in assignment statements. I can't find style guides that discuss this, probably because languages like Java and C# don't allow this at all (their compilers require ternary operators to return a value). Should this be considered a bad use of the ternary statement? Why?

Best Answer

Generally speaking, the conditional operator is intended to make an if statement with a value. w = x ? y : z. Thus, if you're using it for side effects, it's counter-intuitive. Valid, but counter-intuitive; and remember that you're writing code for your teammates to read.

Related Solutions

JavaScript – Ternary Operator vs. ||: Which to Use?

Because this code would evaluate to 'Default Value' everytime you passed in 0, "", false, or some other falsy value.

function fn(param) {
  var paramWithDefault = param || 'Default Value';
  return paramWithDefault;
}

It might not bite you on how you use this particular function, but it is a bad pattern to avoid when you do care about passing in things like empty strings or 0 or a boolean.

Avoiding the New Operator in JavaScript – Better Alternatives

Firstly arguments.callee is deprecated in ES5 strict so we don't use it. The real solution is rather simple.

You don't use new at all.

var Make = function () {
  if (Object.getPrototypeOf(this) !== Make.prototype) {
    var o = Object.create(Make.prototype);
    o.constructor.apply(o, arguments);
    return o;
  }
  ...
}

That's a right pain in the ass right?

Try enhance

var Make = enhance(function () {
  ...
});

var enhance = function (constr) {
  return function () {
    if (Object.getPrototypeOf(this) !== constr.prototype) {
      var o = Object.create(constr.prototype);
      constr.apply(o, arguments);
      return o;
    }
    return constr.apply(this, arguments);
  }
}

Now of course this requires ES5, but everyone uses the ES5-shim right?

You may also be interested in alternative js OO patterns

As an aside you can replace option two with

var Make = function () {
  var that = Object.create(Make.prototype);
  // use that 

  return that;
}

In case you want your own ES5 Object.create shim then it's really easy

Object.create = function (proto) {
  var dummy = function () {};
  dummy.prototype = proto;
  return new dummy;
};

Best Answer

Related Solutions

JavaScript – Ternary Operator vs. ||: Which to Use?

Avoiding the New Operator in JavaScript – Better Alternatives

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