Question 284206 in Javascript Question posted in
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How to re-group an array in javascript?

I have this set of array in my javascript.

var array = [
['Jack', 'A'], 
['Jack', 'A'], 
['Sara', 'A'], 
['Jack', 'B'], 
['Peter', 'B'],
['Sara', 'C'], 
['Sara', 'B'],
['Sara', 'A'],
['Sara', 'B'], 
['Peter', 'B'],
['Peter', 'A'],
['Peter', 'C']
];

my goal is to be arranged like this as an array.

Jack: A : 2
Jack: B : 1
Sara: A : 2
Sara: B : 2
Sara: C : 1
Peter: A : 1
Peter: B : 2
Peter: C : 1

I am trying to code it like this but I can’t get it right

let counts = {};
array.forEach(element => {
     counts[element] = (counts[element] || 0) + 1;
});

does anyone has an idea about this one?
Thank you..

Tags:

2

Answers


  1. 0

    I think you want something like this:

    let array = [
        ['Jack', 'A'], 
        ['Jack', 'A'], 
        ['Sara', 'A'], 
        ['Jack', 'B'], 
        ['Peter', 'B'],
        ['Sara', 'C'], 
        ['Sara', 'B'],
        ['Sara', 'A'],
        ['Sara', 'B'], 
        ['Peter', 'B'],
        ['Peter', 'A'],
        ['Peter', 'C']
    ];

    function transformArray(arr)
    {
        let result = {};

        arr.forEach(function(item) {

            let name = item[0];

            let category = item[1];
    
            if (!result[name]) {
                result[name] = {};
            }
    
            if (!result[name][category]) {
                result[name][category] = 1;
            } else {
                result[name][category]++;
            }
        });
    
        return result;
    }

    console.log(transformArray(array));
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  2. 0

    You could group by both values and map the count.

    const
    data = [['Jack', 'A'], ['Jack', 'A'], ['Sara', 'A'], ['Jack', 'B'], ['Peter', 'B'], ['Sara', 'C'], ['Sara', 'B'], ['Sara', 'A'], ['Sara', 'B'], ['Peter', 'B'], ['Peter', 'A'], ['Peter', 'C']],
    result = Object
        .values(Object.groupBy(data, a => a.join('|')))
        .map(a => [...a[0], a.length]);

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