Pushing array into an array of array in TS

Question

I am coming from Python, and am not entirely familiar with the 'proper' JS/TS way of doing things.

I am looping through the elements of a set, and I am pushing lists of some of the elements onto a 2D array.

let res: number[][];
for (let posElement of posSet) {
    if (negSet.has(-1*posElement)) {
        res.push([-1*posElement, 0, posElement]);
    }
}

I am getting the following error TypeError: Cannot read properties of undefined (reading 'push'). What am I doing wrong, where am I messing up the syntax?

You did not assign any value to res, and as a result its value is undefined. Something that will help you will be to use const everywhere you can - it'll help you catch errors easier — CertainPerformance
– CertainPerformance, Commented Jun 22, 2022 at 4:35
Alright, what are the necessary things I need to do in order to rectify that? It is an empty array that I want to pass things onto. As I said I am coming from Python, and this would be legal code there. — user8814
– user8814, Commented Jun 22, 2022 at 4:37
It is empty, until I need it. What would I assign to it, if it is empty? — user8814
– user8814, Commented Jun 22, 2022 at 4:38

linusw · Accepted Answer · 2022-06-22 04:41:38Z

1

like this initialize

let res: number[][]=[];

answered Jun 22, 2022 at 4:41

linusw

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