JavaScripts read an array that was sent from PHP

Hello I am starting to use JavaScript, I explain my problem, i send array to give from PHP to my JavaScript but when I want to read my array in JavaScript, it reads letter by letter and not words by words.

erreur image

function update(json)
{

    console.log(json);
    var result = JSON.stringify(json);
    console.log(result);

    for (let i =0;i< result.length;i++)
    {
        chart.data.datasets[0].data[i]=result[i];
        console.log(result[i]);
    }
    chart.update();
}
<button data-values="<?php  echo preg_replace('/"/',"'", preg_replace("/'/","'", json_encode($tab[$row]))); ?>" onclick="update(this.getAttribute('data-values'))"><?php echo $worksheet->getCell('A'.$row)->getValue(); ?></button>