为什么我有时会出错，有时不会？

Question

This code is supposed to get random JSON data from an array when the user clicks the button. I'm using a function to return a random number. But when I load the page and click on the button, sometimes I get random data, while sometimes I get an error.

Why is this? Thanks in advance.

$(document).ready(function () {

    function getRandomInt(min, max) {
        return Math.floor(Math.random() * (max - min + 1)) + min;
    }
    
        
    function renderQuiz() {
        console.log(userdata.USER.TOPSONGS[(getRandomInt(0,2))][(getRandomInt(0,4))].snippet);     
    }
    
    ...

    $('#button').click(function () {
        renderQuiz();
        console.log("userprogress: " + userprogress);

        if (userprogress < 10) {
            userprogress++;
            $('#answered').text(`${userprogress} / 10`);
        } 
        else { window.location.href = '/result'; }
        return;
    });

}); //end document.ready

Answer 1

Does userdata.USER.TOPSONGS contain a 3x5 array in which all values are defined and all values have a .snippet ?

Mostly probably, userdata.USER.TOPSONGS does not contain [x][y].snippet for some values 0 <= x <= 2 and 0 <= y <= 4 , causing this error.

Please check your userdata.USER.TOPSONGS array and/or adjust the minimum and maximum values being passed to the random number function.

Answer 2

Looks like reaching out of the boundaries of the array. Your getRandomInt(min, max) returns random int including min and max values. Check if this is okay.