What is the proper way to initialize a two-dimensional array in JavaScript?

I recently received a suggestion on this question to create a two-dimensional array in my jQuery quiz application. However, I seem to be encountering an error while running the code. I suspect the issue might be due to incorrect formatting or a lack of initialization.

Uncaught TypeError: Cannot set property '1' of undefined

Below is a snippet of my current code:

var answers = [];
answers [0] = [];
answers[0][1] = accept; answers[0][2] = wrong; answers[0][3] = wrong; 
answers[1][1] = wrong; answers[1][2] = best; answers[1][3] = wrong;
javascriptarrays

Answer №1

Don't forget to initialize all your variables, especially array[1].

Check out this updated version of your code:

var answers = [];
answers[0] = [];
answers[1] = [];
answers[0][1] = accept;
answers[0][2] = wrong;
answers[0][3] = wrong; 
answers[1][1] = wrong;
answers[1][2] = best;
answers[1][3] = wrong;

Answer №2

Should you decide to hardcode the components in such a way, you have the option of implementing this technique:

var responses = [
    [correct, incorrect, incorrect],
    [incorrect, optimal, incorrect]
];

It is presumed that correct, incorrect, and optimal are variables.

Answer №3

To avoid the hassle of checking if the array has been initialized, you can simply initialize it if it hasn't been defined yet. Here's how you can do it:

function addElement(arr, path, val) {
  path.forEach(function(index, position) {
    if (arr[index] === undefined) arr[index] = [];
    if (position < path.length - 1) arr = arr[index];
    else arr[index] = val;
  });
}

var data = [];
addElement(data, [2, 4, 6], "approved");
alert(data[2][4][6]); // approved

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