How can I avoid nested ternary expressions in my code?

user_8604111 0
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I have code like this. How can I write it in cleaner, more elegant way using functional programming in JavaScript? I want to get rid of nested ternary expressions. Any ideas?

props => ({
            iconColor: props.isPriority ? (props.isCompleted ? variables.color.lightpurple : variables.color.purple ) : variables.color.gray3,
            iconName: props.isPriority ? 'star-full' : 'star-empty',
          }))

This is rest of that code:

EDIT:

const enhance: React$HOC<*, InitialProps> = compose(
      withProps(props => ({
        iconColor: props.isPriority ? (props.isCompleted ? variables.color.lightpurple : variables.color.purple) : variables.color.gray3,
        iconName: props.isPriority ? 'star-full' : 'star-empty',
      }))
    )
purely-functional functional-programming javascript
5 Answers

Yes, but my linter is not happy: 44:16 error Do not nest ternary expressions [no-nested-ternary]

If that's your only problem then the solution is simple. Create your own conditional function:

const iff = (condition, then, otherwise) => condition ? then : otherwise;

props => ({
  iconColor: props.isPriority ?
    iff(props.isCompleted, variables.color.lightpurple, variables.color.purple) :
    variables.color.gray3,
  iconName: props.isPriority ? 'star-full' : 'star-empty',
})

Now your linter shouldn't complain. That being said, you should disable [no-nested-ternary] in your linter. It's kind of stupid that your linter thinks that nested conditionals are bad.

user_7837430

In this case you could consider inverting the condition to remove the "unnatural" nesting of ternaries. There would still be nesting, but it can be written flat - without parentheses - which means that you can lay it out neatly across multiple lines:

props => ({
    iconColor:
        !props.isPriority ? variables.color.gray3
        : props.isCompleted ? variables.color.lightpurple
        : variables.color.purple,
    iconName: props.isPriority ? 'star-full' : 'star-empty',
})

The downside of this is use of a negative condition, which I usually try to avoid as they're a bit harder to follow than positive conditions.

Yet another option is to flatten the conditions with &&:

props => ({
    iconColor:
        props.isPriority && props.isCompleted ? variables.color.lightpurple
        : props.isPriority ? variables.color.purple
        : variables.color.gray3,
    iconName: props.isPriority ? 'star-full' : 'star-empty',
})
user_6096390

I will suggest, simply use below:

    props => ({
      iconColor: ${(props) => {
      if (props.isPriority) {
        return props.isCompleted
          ? variables.color.lightpurple
          : variables.color.purple;
      }
      return variables.color.gray3;
    }};
      iconName: props.isPriority ? 'star-full' : 'star-empty',
    })
user_62987150
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