CODEWITHSUNDEEP
javascriptarraysobject
Nathan Boaldin
Nathan Boaldin

Reputation: 315

How do I make an object with a given key and value?

I am trying to create a function that returns a new object with a key–value pair. I am getting the key and value from the first and last elements of an array. I can get the function to return the elements that will make up the key–value pair, but as soon as I wrap the array elements in curly braces to return an object via the function, it doesn’t work. What is the problem?

// Create an array
var names = ["Apples", "Oranges", "Yummy", "Candy", "Plop"];

// Return an object with a key–value pair from the first and last element of an array
function firstLast(array) { 
  var obj = {
     array[0] + ": " + "'" + array[array.length - 1] + "'";
  };
  return obj;
}

console.log(firstLast(names));

Upvotes: 0

Views: 45

Answers (2)

gavgrif
gavgrif

Reputation: 15499

You can use square brackets notation to assign the value, but my initial post contained the same answer as @Xufox's alternative. So I thought I would present a different approach that uses the arguments that are passed into the function and build the returned object from shifting and popping from that array. Just a different wy of doing the same job.

var names = ["Apples", "Oranges", "Yummy", "Candy", "Plop"];

function firstLast(array) { 
  return {[arguments[0].shift()]: arguments[0].pop()};
}

console.log(firstLast(names));

Upvotes: 1

Sebastian Simon
Sebastian Simon

Reputation: 19475

That’s invalid syntax. What you need is this:

var obj = {
  [array[0]]: array[array.length - 1]
};

This uses computed properties.

An alternative would be:

var obj = {};
obj[array[0]] = array[array.length - 1];

Upvotes: 4

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