Add value to object from array and not become undefined when array runs out

Question

I have a function with params and I am doing a forEach loop to add all the values from the loop.

const data = (sd) => Object.entries(obj).map(([k, g]) => ({
            ['name']: k,
            ['data']: g.map(entry => entry[sd]),
            ['type']: sd
        }));

I then push them into a giant array:

let arr = ['abc', 'xyz'];
let x = [];
arr.forEach(y => {
  x = [...x, ...data(y)];
});

I also want to add another key-value pair to data. I want the value to come from an array:

color_array = ['red', 'blue', 'green']

So I did:

const data = (sd) => Object.entries(obj).map(([k, g]) => ({
            ['name']: k,
            ['data']: g.map(entry => entry[sd]),
            ['type']: sd,
            ['color']: color_arr[i++]
        }));

Output:

color: "red"
data: (3) [1, 2, 3]
name: "Jim"
type: "Manager"

color: "blue"
data: (3) [1, 2, 3]
name: "Steve"
type: "Manager"

color: "green"
data: (3) [1, 2, 3]
name: "John"
type: "Manager"
--------------------NEW SET----------------
color: undefined
data: (3) [1, 2, 3]
name: "John"
type: "CEO"

color: undefined
data: (3) [1, 2, 3]
name: "John"
type: "COO"

When I do this, since I only have 5 elements in my array, the rest of the values go undefined. Is there any way for me to add elements from the array to start from the beginning of the color_arr?

I mean, for every x = [...x, ...data(y)];, Can the colors being added to data(y), always start from red, rather than just be valued as undefined?

why not take name instead of a computed property name with a string of ['name']? do you have an example of input an wanted output? — Nina Scholz
– Nina Scholz, Commented May 10, 2020 at 19:56

Ed Lucas · Accepted Answer · 2020-05-10 20:19:03Z

1

You can loop over the values in the color array by using the modulo. That is, the remainder of dividing your counter by the color array's length.

const color_array = ['red', 'blue', 'green', 'black', 'white'];
let i = 0;
for (j = 0; j < 20; j++) {
   console.log(color_array[i++ % color_array.length]);
}

Untested version of your code:

const data = (sd) => Object.entries(obj).map(([k, g]) => ({
        ['name']: k,
        ['data']: g.map(entry => entry[sd]),
        ['type']: sd,
        ['color']: color_array[i++ % color_array.length]
}));

More information on the % operator: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Remainder

edited May 10, 2020 at 20:19

answered May 10, 2020 at 20:03

Ed Lucas

7,4544 gold badges40 silver badges52 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

nb_nb_nb Over a year ago

Is there any way to restart the array with every x = [...x, ...data(y)];. So every time data(y) is pushed, Can the values from color array being added start from the beginning?

Ed Lucas Over a year ago

You can reset i = 0 inside your loop.

nb_nb_nb Over a year ago

Sorry, how do I do that?

Ed Lucas Over a year ago

You can define the variable i above your loop instead and set it to zero for each y. For example: let i; arr.forEach(y => { i = 0; x = [...x, ...data(y)]; });

Collectives™ on Stack Overflow

Add value to object from array and not become undefined when array runs out

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related