Trying to figure out what the ? and : mean in this one line return statement.
return input && input.length ? [input.filter(p => p > 0).length, input.filter(n => n < 0).reduce((a, b) => a + b, 0)] : [];
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Jeff
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6Ternary operator. Google it. – Robby Cornelissen Jan 20 '17 at 03:23
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1"In computer science, a ternary operator is an operator that takes three arguments." It's probably better to Google conditional operator. – Bill the Lizard Jan 20 '17 at 03:26
3 Answers
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This is a ternary if statement, I'd use parenthesis for organization sake, but it works like this:
[condition] ? [returns if condition is true] : [returns if condition is false]
bestafubana
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In his case the condition is wether `input` is defined and has the property `length`. – ibrahim mahrir Jan 20 '17 at 03:28
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It means that if the condition before ? is true then use the first part before : else use the second part.
In your case it means that if input is not null and has value, then return the filtered one otherwise return an empty array.
Yaser
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In the OP it will return an array of `[a, b]` where *a* is the number of elements greater than zero and *b* is their sum, or `[]` (empty array). – RobG Jan 20 '17 at 03:41