Using JS reduce() on base of map()

user_8851869 0
Viewed 73

I have this array of objects:

let authors = [
  { firstName: "Beatrix", lastName: "Potter" },
  { firstName: "Ann", lastName: "Martin" },
];

I want to unify the details after mapping the array items with map(), then reduce the objects to a single string with reduce() so the output would be "Beatrix Potter", "Ann Martin".

I have tried the following code but failed:

fullAuthorNames = authors.map( (e)=> 
    authors.reduce( (firstName, lastName)=> firstName + lastName );
);

This is the relevant output:

["[object Object][object Object][object Object][object Object][object Object]","[object Object][object Object][object Object][object Object][object Object]"

What did I do wrong here? Maybe I didn't target the objects inside the array right?

javascript
3 Answers

You won't need a reduce, just map then join the result array:

let fullAuthorNames = authors.map(a => a.firstName + " " + a.lastName).join(", ");

Example:

let authors = [
  { firstName: "Beatrix", lastName: "Potter" },
  { firstName: "Ann", lastName: "Martin" },
];


let fullAuthorNames = authors.map(a => a.firstName + " " + a.lastName).join(", ");

console.log(fullAuthorNames);

user_98674510

Map the each object to a string using a template literal, and join the results to a string:

const authors = [
  { firstName: "Beatrix", lastName: "Potter" },
  { firstName: "Ann", lastName: "Martin" },
];

const result = authors.map(({ firstName, lastName }) => `${firstName} ${lastName}`)
  .join(', '); // remove this if you want an array of strings

console.log(result);

user_51574540

Array.Map converts an array to another array. Array.Reduce aggregates an array into a value. They're typically used in serial.

Try:

fullAuthorNames = authors.map(  (e)=> e.firstName + ' ' + e.lastName )
                         .reduce((accumulator, currentValue, index) =>
                                  accumulator + (index ? ', ' : '') + currentValue, '');

'join', as in the answers above is probably simpler, but not quite what you asked.

user_13060260
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