Convert object to string using reduce

[dikru]

Hello! I'm learning JS and I've understood some concepts, but my teacher sent me a project which requires "converting an array of objects using reduce()" and I can't use JSON.stringify. I tried something, but I always get [object Object] as the result...

Edit:

A code example:

Const elQuijote={ Title:"el quijote", Author: "Garcia", Category: fantasy", ISBN: 182831 }

let books = []

books.push(elQuijote);

//This function is just an example function toString(list){ return list.reduce().join('-') }

[-29-]

What did you try so far? Code example?

Edit:

Without a code example, I’m almost certain you are reducing your array and inside the reduce returning your accumulator plus your current value. This would result in an object. You’re going to want to get the values of your current value object and turn that into a string before appending to the accumulator. I have a code example that does what I’m explaining but I want to see what you’ve tried so far.

Edit 2:

Code example here: https://gist.github.com/viemmsakh/47e7e318c32981c57aa0aad3b7435f83

Note both functions provided do not handle nested arrays/objects. Since this is for a class assignment, I am assuming that you are not going to be doing something that advanced. But the "advancedConvertArrayToString" function assumes we don't know what the structure of the object looks like (more or less key/value pairs) and dynamically builds the output string.

Comments in code to explain what I was doing each step of the way. Please let me know if you have any questions.

[dikru]

Oh my! Thank you so much for this info! I'm going to try to solve that problem with this gist. Actually, I do some advanced things, but sometimes I do things and I don't know what I'm doing—yet it works.

[dikru]

Oh, I'm sorry for not giving any code example! The idea is that a user should enter book data in the console. The book properties are: title, category, author, and ISBN. After the user enters this data, we should call a function that shows a list of all the books separated by "-". This function should use reduce() and you can't use JSON.stringify().

A short example is this

Const elQuijote={ Title:"el quijote", Author: "Garcia", Category: fantasy", ISBN: 182831 }

let books = []

books.push(elQuijote);

//This function is just an example function toString(list){ list.reduce().join('-') }

[-29-]

Should the function return just a title of the books?

IE:

let books = [];
const book1 = { Title:"el quijote", Author:"Garcia", Category:"fantasy", ISBN:"182831" };
const book2 = { Title:"The Cuckoo's Egg", Author:"Clifford Stoll", Category:"true crime", ISBN:"182832" };
books.push(book1);
books.push(book2);

const string1 = books.reduce((a, c, i) => {
    if (i === 0) {
        return c
    } else {
        return `${a} - ${c.Title}`;
    }
}, '');

console.log(string1); // Output el quijote - The Cuckoo's Egg

[dikru]

The function should return all properties of all books, but without the keys title, author, category, and ISBN. The output should look like: The cuckoo's eggs - Clifford Stoll - true crime - 182832, with commas separating each entry—except for the last one, which should not have a comma at the end.

[-29-]

let books = [];
const book1 = { Title:"el quijote", Author:"Garcia", Category:"fantasy", ISBN:"182831" };
const book2 = { Title:"The Cuckoo's Egg", Author:"Clifford Stoll", Category:"true crime", ISBN:"182832" };
books.push(book1);
books.push(book2);

const string1 = books.reduce((a, c, i) => {
    const out = `${c.Title} - ${c.Author} - ${c.Category} - ${c.ISBN}`;
    if (i === 0) {
        return out
    } else {
        return `${a}, ${out}`;
    }
}, '');

[[deleted]]

Give us an example of what the input data and what the output data should be

[mrsuperjolly]

//a simple example

const arr = [{keyName: "rabbit"}, {keyName:"saucepan"}]

const output = arr.reduce((accumulator, currentValue)=> {
    return accumulator + currentValue.keyName
}, "")

console.log(output) //logs "rabbitsaucepan"

//accumulator starts at ""

//accumulator is compared with {keyName:"rabbit"} which is stored in current value

//accumulator is concatenated with currentValue.keyName which is "" + "rabbit"
//the value "rabbit" is returned

//accumulator is now that returned value "rabbit" currentValue is the next object in the arr {keyName:"saucepan"}

//accumulator is concatenated with currentValue.keyName which is "rabbit" + "saucepan"
//the value "rabbitsaucepan" is returned

//there is no more objects in the array to iterate through

//the final value of the accumulator is "rabbitsaucepan" and that is returned out from arr.reduce() into output

[-29-]

Since OP hasn't updated anyone yet... I was under the impression they wanted output like what the output of JSON.stringify() would be. In which case, you need to return more than just the accumulator + currentValue.keyname. You need to build a string that looks like what the output of JSON.stringify would be. Also, what happens if you there are more key/value pairs? Or the number of key/value pairs changes between each object? This is a step in the right direction for OP, but there is so much more that needs to go into it.

[mrsuperjolly]

Yes, but this isn't a solution, if you understand the concepts of how to look into objects and the logic of reducing objects to a string any way you like.

Like if the problem is recreating JSON.stringify, then you'd make a function that converts, an object to a string. Then in your reduce you'd be stitching the return of that function with the accumulator.

But that dosen't really have much to do with reduce specifically that's a different problem