JavaScript Array Manipulations

Manipulating 2d, 3d, or 4d arrays in JavaScript are necessary for AI model training and image/audio/video analysis.

Below are a few useful functions for array manipulation using pure JavaScript without matrix packages like Tensorflow.js.

Transpose of a 2d array

function transpose_2d_array(arr) {

    var transpose_colNum = arr.length;
    var transpose_rowNum = arr.at(0).length;
    var transpose_arr = [];
    for (var i=0; i<transpose_rowNum ; i++) {
        const col = Array.from({ length: transpose_colNum }, (_, i) => 0);
        transpose_arr.push(col);
    }

    for (var i=0; i<arr.length; i++) {
        for (var j=0; j<arr.at(i).length; j++) {
            transpose_arr[j][i] = arr[i][j];
        }
    }
    return transpose_arr;
}

Print the Shape of an array

async function recur_func(arr) {
    if (arr != undefined) {
        return [arr[0], arr.length];
    } else {
        return arr;
    }
}

async function shape(arr) {
    var out = await recur_func(arr);
    var shap = [out[1]];
    var c = 0; // typically work with 4D arrays or less
    while (out != undefined && c < 4) {
        out = await recur_func(out[0]);
        if (out != undefined) {
            shap.push(out[1]);
        }
        c = c + 1;
    }
    return shap.slice(0, shap.length-1);
}

I hope these array utility functions will be helpful to someone.

Happy practicing! ?

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