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problem with javascript array assignment, how can " == true : false" working in this code?

I am studying javascript and here is my problem.

They gave me the variable named "couldBeAnything" which can be any data type. And another variable which named result, too. I must check if the given variable is array then assign true to result. Other cases then false to result. Here is the code.

function checkIsArray(couldBeAnything) {
var result = true ? Array.isArray(couldBeAnything) == true : false
return result;
}

Sorry for my wonder, because this code is from my senior, so I can not understand it clearly, I just only understand if else, so could you please explain this code for me ? How dose it work ? Thank you very much.

3 months ago ·

Juan Pablo Isaza

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Answer 1 · 2022-07-11T11:33:24.327Z

This is working because it's doing several pointless operations that complicate reading it, but it's really just using Array.isArray.

Array.isArray(couldBeAnything) == true

If an array is passed in, Array.isArray is true, true == true is true.

So what you get is, if an array is passed in:

var result = true ? true : false;

Which is true.

And for a non-array:

var result = true ? false : false;

Which is false.

This is hopefully the result of several refactorings or lazy merges, because writing this on purpose is pretty silly as others have stated.

Answer 2 · 2022-07-11T11:33:24.333Z

I think you are have not been exposed to ternary operators.

let x=true
let result
if(x){
  result="Thats true"
}
else{
  result="No thats false"
}
console.log(result)

The above can be written as

let x=true
let result=x?"That's true":"No that's false"
console.log(result)

The logic is that if the expression before ? is true then the code after the ? will be executed and if it's false then the code after : will be executed.

That's simple, right?

In your case the code is wrong. It should be like this:

function checkIsArray(couldBeAnything) {
 var result = Array.isArray(couldBeAnything) ? true : false
 return result;
}

But there is no need for ternary conditions here. You can directly use this

function checkIsArray(couldBeAnything) {
   return Array.isArray(couldBeAnything)
}