Loop to create array + loop increment?

Question

I wanted to create a function which gets called upon-page load and generates a graph based on what user inputs (multiple datasets, using chart.js).

Decided to rely on prompt() for initial testing, but soon ran into a problem.

function defineDatasets(itt){
    for(i=0; i<itt; i++){
        var dataSet+i=[]; // <--- Does not result in a array called "dataSet0[], ..." etc
    }
}

So my question is, if and how could this be achieved?

Bucket · Accepted Answer · 2018-07-17 19:11:31Z

2

If you're trying to suffix your arrays with an index, why not just make an array of arrays? Also be sure to define your dataSet outside the function scope:

let dataSet = [];

function defineDatasets(itt) {
    for(var i = 0; i < itt; i++) {
        dataSet.push([]);
    }
}

console.log(dataSet[0]); // []

Now instead of referencing these arrays with dataSetN, you can do dataSet[N], where N is the Nth dataSet index.

edited Jul 17, 2018 at 19:11

answered Jul 17, 2018 at 18:22

Bucket

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3 Comments

Patrick Roberts Over a year ago

It might be beneficial to dataSet = []; before the for loop so that multiple calls to defineDatasets() does not append more empty arrays to dataSet if it's already been initialized.

Bucket Over a year ago

@PatrickRoberts - True. Alternatively, changing dataSet.push([]) to dataSet[i] = [] would mitigate this issue.

Patrick Roberts Over a year ago

That'd actually be even worse. Consider

defineDatasets(20); /* do stuff with dataSet... */ defineDatasets(10); /* expect dataSet.length === 10, but it's actually still 20 */

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