Javascript: How to insert a hole into a sparse array or creating a hole

user_12866719 0
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I'm using sparse arrays to be memory efficient with huge datasets. (and to signal the difference between a hole and a undefined or null entry) adding holes at the end is fine by setting datapoints.lentgh.

datapoints = [10,,,20,,,10,1]

No I face the problem how to insert a hole (say before 20)

datapoint.splice(3,0)

does not work, and I can't find a (easy) method to insert holes. (Think I have to rebuild the array but thought to ask before) Or is there a way to change a "defined" entry into a hole? delete datapoint[4]; creates an undefined entry not a hole :(

sparse-matrix arrays javascript
2 Answers

Your sparse array is actually an object. You can delete items and you can add items.

Let's suppose you want to add k holes before position offset. Then:

datapoints = [10,,,20,,,10,1];
function addHoles(offset, k, datapoints) {
    let migration = {};
    for (let key in datapoints) {
        let intKey = parseInt(key);
        if (intKey >= offset) {
            migration[intKey] = datapoints[intKey];
            delete datapoints[intKey];
        }
    }
    for (let key in migration) {
        let intKey = parseInt(key);
        datapoints[intKey + k] = migration[intKey];
    }
    return datapoints;
}
console.log(addHoles(3, 3, datapoints));

user_4365600

Think I could work with

datapoint.splice(3,0,undefined);
delete datapoint[3]

It looks like that I have a hole now ....

user_128667190
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