I’m trying to pick a random value for each row of the array in js, however when i run the code i get Uncaught TypeError: can’t access property "innerHTML", document.getElementById(…) is null even though the script is at the bottom of
<p id="crit1"></p>
<p id="crit2"></p>
<p id="crit3"></p>
<p id="crit4"></p>
<p id="crit5"></p>
<script>
var criteria = [
['opt1', 'opt2'],
['opt3', 'opt4'],
['opt5', 'opt6'],
['opt7', 'opt8'],
['opt9', 'opt10']
];
for (var step = 0; step <5; step++){
var rand = Math.round(Math.random()); //genrates either 0 or 1
if (rand == 1) {
document.getElementById('crit'+ step).innerHTML = criteria[step][1];
var answ = answ +1;
} else {
document.getElementById('crit'+ step).innerHTML = criteria[step][0];
}
}
>Solution :
It’s failing because your step counter starts at 0 but you have no element with ID crit0.
If you add a crit0 element or start your counter at 1, the error goes away.
It can also be helpful to also include a null check for document.getElementByID() to avoid throwing errors when it can’t find the element:
const critElement = document.getElementById('crit' + step);
if (critElement) {
critElement.innerHTML = criteria[step][0];
}