How to print a new array from existing array of object javascript

Question

I need to create a new array of objects from the existing array on vuejs.

example first array :

import { ref } from 'vue';

const base_array = ref([
  {id: 1, name: Pill, timing: [morning, noon, evening, night]},
  {id: 2, name: Tablet, timing: [morning, evening]},
])

expected result :

const modified_array = ref([
  {id: 1, name: Pill, timing: [morning]},
  {id: 2, name: Pill, timing: [noon]},
  {id: 3, name: Pill, timing: [evening]},
  {id: 4, name: Pill, timing: [night]},
  {id: 5, name: Tablet, timing: [morning]},
  {id: 6, name: Tablet, timing: [evening]},
])

I've tried forEach and looping the array, but seems can't find the right function. Thank youu

did you want modified_array to change when base_array changes? — Bravo
– Bravo, Commented Jul 4, 2022 at 10:04

Milos Pavlovic · Accepted Answer · 2022-07-04 10:52:28Z

3

Using flatMap, something like this:

const base_array = ref([
      { id: 1, name: Pill, timing: [morning, noon, evening, night] },
      { id: 2, name: Tablet, timing: [morning, evening] },
    ]);

const modified_array  = ref(base_array.value.flatMap(el => el.timing.map(t => ({id: el.id, name: el.name, timing: [t]}))));

edited Jul 4, 2022 at 10:52

answered Jul 4, 2022 at 10:02

Milos Pavlovic

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Comments

Bravo · Accepted Answer · 2022-07-04 10:24:12Z

This code should work

const modified_array = ref(
    base_array.value.flatMap(({timing, ...r}) =>
        timing.map(timing => ({...r, timing:[timing]}))
    )
);

However, if you want modified_array to be reactive to changes in base_array - you'd want to use computed not ref for modified_array as in the code snippet below

If you watch, then the modified_array output changes when the base_array changes after three seconds with this code

setTimeout(() => base_array.value[1].timing.push('reactive!!!'), 3000);

Anyway, here's the example of fully functional code for vue3

const { ref, createApp, computed } = Vue;


createApp({
    setup() {
        const base_array = ref([
          {id: 1, name: 'Pill', timing: ['morning', 'noon', 'evening', 'night']},
          {id: 2, name: 'Tablet', timing: ['morning', 'evening']},
        ]);
        const modified_array = computed(() =>
            base_array.value.flatMap(({ timing, ...r }) =>
                timing.map((t) => ({ ...r, timing: [t] }))
            )
        );
        setTimeout(() => base_array.value[1].timing.push('reactive!!!'), 3000);
        return { base_array, modified_array};
    }
    
}).mount('#app');

.as-console-wrapper { max-height: 0 !important; top: 0; }

<script src="https://unpkg.com/vue@next"></script>

<div id="app">
  <ul>
    <li v-for="({id, name}) in base_array" :key="id">
    {{ id }}: {{ name }}
    </li>
  </ul>
  <ul>
    <li v-for="({id, name, timing}, i) in modified_array" :key="i">
    {{ id }}: {{ name }} {{timing[0]}} 
    </li>
  </ul>
</div>

Rohìt Jíndal · Accepted Answer · 2022-07-04 13:40:38Z

0

You can simply achieve that by using Array.forEach() along with the Destructuring assignment.

Live Demo :

const base_array = [
  {id: 1, name: 'Pill', timing: ['morning', 'noon', 'evening', 'night']},
  {id: 2, name: 'Tablet', timing: ['morning', 'evening']},
];

let modified_arr = [];
let index = 1;

base_array.forEach(obj => {
    const {id, name, timing} = obj;
  timing.forEach(t => {
    modified_arr.push({ id: index, name, timing: [t]})
    index++;
  })
});

console.log(modified_arr);

answered Jul 4, 2022 at 13:40

Rohìt Jíndal

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