JavaScript: order array by taking alternately an object of each type

Question

I have an array of objects like this (ordered by type, the objects of the same type are identical):

[
    { "type":"A", "height":50, "width":80 },
    { "type":"A", "height":50, "width":80 },
    { "type":"B", "height":20, "width":100 },
    { "type":"B", "height":20, "width":100 },
    { "type":"C", "height":90, "width":10 }
]

I want to have all these objects in an array which is ordered by taking alternately an object of each type:

[
    { "type":"A", "height":50, "width":80 },
    { "type":"B", "height":20, "width":100 },
    { "type":"C", "height":90, "width":10 },
    { "type":"A", "height":50, "width":80 },
    { "type":"B", "height":20, "width":100 }
]

Answer 1

You could take a Map and iterate until all items are processed in the right order.

var array = [{ type: "A", height: 50, width: 80 }, { type: "A", height: 50, width: 80 }, { type: "B", height: 20, width: 100 }, { type: "B", height: 20, width: 100 }, { type: "C", height: 90, width: 10 }],
    order = ['A', 'B', 'C'],
    types = new Map(order.map(k => [k, []])),
    result = [];

array.forEach(o => types.get(o.type).push(o));

while (types.size) {
    types.forEach((a, k) => (result.push(a.shift()), a.length || types.delete(k)));
}

console.log(result);

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