How do languages handle removing objects during iteration?

javascript.js

var list = [1, 2, 3, 4];
list.forEach(function(entry) { 
  console.log(entry); 
  var index = list.indexOf(entry); 
  list.splice(index, 1); 
});
console.log('list after loop: ', list);

/**
Console output: 
> 1
> 3
> list after loop: [2, 4]
*/

objc.m

NSMutableArray<NSNumber *> *list = [[NSMutableArray alloc] initWithArray:@[@(1), @(2), @(3), @(4)]];
    
[list enumerateObjectsUsingBlock:^(NSNumber * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
    NSLog(@"object: %@", obj);
    [list removeObject:obj];
}];
NSLog(@"list after loop: %@", list);

/**
Console output:
> object: 1
> object: 3
> list after loop: (
    2,
    4
)

*/

swift.swift

var list: [Int] = [1, 2, 3, 4]
        
for (index, object) in list.enumerate() {
    print(object)
    list.removeAtIndex(index)
}
print("list after loop: \(list)")


/**
Console output:
> 1
> 2
> 3
> fatal error: Index out of range
*/