JavaScript recursive operation array

Question

I have an array like this (arr), how do I want to get an array like (arr2)? Where the 'start' and 'end' elements are fixed values。

Original array：

var arr = [
  {form: 'start', to: 'task-1'},
  {form: 'start', to: 'task-4'},
  {form: 'task-1', to: 'task-2'},
  {form: 'task-2', to: 'end'},
  {form: 'task-1', to: 'task-3'}
]
console.log(arr)

Expected array：

var arr2 = [
  {form: 'start', to: 'task-1'},
  {form: 'task-1', to: 'task-2'},
  {form: 'task-2', to: 'end'},
]
console.log(arr2)

Basically, you have a graph here. So use one of the more common graph representations and run a (breadth|depth)-first-search on it. — Sirko
– Sirko, Commented Jan 17, 2020 at 5:31
may be your expected array list seems like group by 'form' and first record 'to', Am i correct.? — Chandrashekhar Komati
– Chandrashekhar Komati, Commented Jan 17, 2020 at 5:35
@chandukomati Yes, the first is form: start and the last is to: end — 25757750
– 25757750, Commented Jan 17, 2020 at 5:38

Siva Kondapi Venkata · Accepted Answer · 2020-01-17 05:58:08Z

1

Recursively find object and push to result array. Here is sample code.

var arr = [
  {form: 'start', to: 'task-1'},
  {form: 'start', to: 'task-4'},
  {form: 'task-1', to: 'task-2'},
  {form: 'task-2', to: 'end'},
  {form: 'task-1', to: 'task-3'}
]


const getTo = search => arr.find(x => x.form === search).to;

let form = 'start';
let to = '';
const res = [];

while (to !== 'end') {
  to = getTo(form);
  res.push({form, to});
  form = to;
}

console.log(res)

answered Jan 17, 2020 at 5:58

Siva Kondapi Venkata

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2 Comments

Sirko Over a year ago

This seems to assume, that there is only one element per form entry. How does your algorithm cope with the duplicates like the two from: 'task-1' elements?

Siva Kondapi Venkata Over a year ago

@Sirko, Yes, my assumption is that finds the first element in duplicates. Based on the output mentioned in question and summary, "recursive " approach to get the path, this will be sample solution. Agree that this will not address duplicates. There can be lot of variations to it, getting all possible paths, or get short path (less nodes) or long path etc.

CHANist · Accepted Answer · 2020-01-17 05:47:53Z

0

Here is it.

var arr = [
  {form: 'start', to: 'task-1'},
  {form: 'start', to: 'task-4'},
  {form: 'task-1', to: 'task-2'},
  {form: 'task-2', to: 'end'},
  {form: 'task-1', to: 'task-3'}
]
// console.log(arr);

const obj = arr.reduce((accum, value) => {
    const formId = value.form; 
    const to = value.to; 
    if (!accum[formId]) {
        accum[formId] = to;
    }
    return accum;
}, {});

const arr2 = Object.entries(obj).map(([key, value]) => {
    return {
        form: key, 
        to: value
    }
});
console.log(arr2);

answered Jan 17, 2020 at 5:47

CHANist

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2 Comments

Sirko Over a year ago

There are duplicates for from in the input. Doesn't you lookup ignore those? So if the order of entries in the input changed, you algorithm would not work anymore, I guess.

CHANist Over a year ago

Sorry, you are correct, I misunderstand the question. :( Thanks

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