Checkout page could hang for Javascript error

[angelo983]

Description

Wrong evaluating check comparison with 'undefined' of variable 'position' let hang Checkout Page
https://stackoverflow.com/a/5076962 (difference between null and undefined in JavaScript)

Fixed Issues (if relevant)

in lib/web/mage/utils/arrays.js
Line 104 to 128

if (typeof position === 'undefined') { // line 104 - fixed issue transcribed below
    position = -1;
} else if (typeof position === 'string') {
    position = isNaN(+position) ? position : +position;
}

newIndex = position;

if (~currentIndex) {
    target = container.splice(currentIndex, 1)[0];

    if (typeof item === 'string') {
        item = target;
    }
}

if (typeof position !== 'number') {
    target = position.after || position.before || position; // line 121

    newIndex = getIndex(target, container);

    if (~newIndex && (position.after || newIndex >= currentIndex)) {
        newIndex++;
    }
}

Error in line 121 because position value is NULL and this value is not managed in the script

This is the only change to apply:
lib/web/mage/utils/arrays.js
Line 104
from
if (typeof position === 'undefined') {
to
if (typeof position === 'undefined' || position == null) {

Contribution checklist

• Evidence of faulty javascript comparison
• https://stackoverflow.com/a/5076962

[magento-cicd2]

All committers have signed the CLA.

[orlangur]

Please provide additional details in the issue itself.

[angelo983]

@orlangur I believe instead that the programmer who wrote that line of code made the one mistake as expressed in the link https://stackoverflow.com/a/5076962 (difference between null and undefined in JavaScript).
If you are not convinced of this, state in what scenario the position should be of undefined type since that case is handled in the code
Summary:

Why YES?
if (typeof position === 'undefined') {

(My proposal)
if (typeof position === 'undefined' || position == null) {

[angelo983]

Hello, still updates needed?

[orlangur]

#9984 needs to be rechecked first.