Question 51766 in Javascript Question posted in
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How to create separate arrays from a parent object array – Javascript

Suppose I have an object that looks like this

const parent_obj = {
  'metrics': [
    ['2023-03-28 15:40:00+00:00', 1692.1, 1.0],
    ['2023-02-28 15:40:00+00:00', 1211.6, 0.0],
    ['2023-01-28 15:40:00+00:00', 763.1, 1.0]
  ]
};

I want to have 2 arrays that look like this:

var duration = {
  'metrics': [
    ['2023-03-28 15:40:00+00:00', 1692.1],
    ['2023-02-28 15:40:00+00:00', 1211.6],
    ['2023-01-28 15:40:00+00:00', 763.1]
  ]
};
var error_ratio = {
  'metrics': [
    ['2023-03-28 15:40:00+00:00', 1.0],
    ['2023-02-28 15:40:00+00:00', 0.0],
    ['2023-01-28 15:40:00+00:00', 1.0]
  ]
};

I basically want to iterate through the metrics list and get index 0 and 1 for duration and 0 and 2 for error_ratio. What is the easiest way to accomplish this goal using vanilla javascript?

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4

Answers


  1. 0

    You can define helper function that use map to get the data by index:

    const parent_obj = {
  'metrics': [
    ['2023-03-28 15:40:00+00:00', 1692.1, 1.0],
    ['2023-02-28 15:40:00+00:00', 1211.6, 0.0],
    ['2023-01-28 15:40:00+00:00', 763.1, 1.0],
  ],
};

const getMetrics = (data, indexes) => ({
  'metrics': data.metrics.map(entry => indexes.map(index => entry[index])),
});

const duration = getMetrics(parent_obj, [0, 1]);
const error_ratio = getMetrics(parent_obj, [0, 2]);

console.log(duration);
console.log(error_ratio);
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  2. 0

    The simplest way is using the map method

    const duration = {
  'metrics': parent_obj.metrics.map(metric => [metric[0], metric[1]])
};

const error_ratio = {
  'metrics': parent_obj.metrics.map(metric => [metric[0], metric[2]])
};
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  3. 0

    You could take an helper array dor the groups and indices and map.

    const
    metrics = [['2023-03-28 15:40:00+00:00', 1692.1, 1.0], ['2023-02-28 15:40:00+00:00', 1211.6, 0.0], ['2023-01-28 15:40:00+00:00', 763.1, 1.0]],
    indices = [[0, 1], [0, 2]];
    duration = {},
    error_ratio = {};

[duration.metrics, error_ratio.metrics] = indices.map(ii => metrics.map(m => ii.map(i => m[i])));

console.log(duration);
console.log(error_ratio);
    .as-console-wrapper { max-height: 100% !important; top: 0; }
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  4. 0

    You can use the javascript built-in Array.reduce() function like the one below. I think it will work for you.

    let { duration, error_ratio } = parent_obj.metrics.reduce((data, item)=>{
    data.duration.push([item[0],item[1]])
    data.error_ratio.push([item[0],item[2]])
    return data
},{
    duration: [],
    error_ratio: []
})

    More clarification about Array.reduce() visit this link https://www.programiz.com/javascript/library/array/reduce

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