how to push element into array at specific index in loop

Question

When i try:

for (index = 0; index < results[1].length; ++index) {
          results[1].splice(index,0,{Keys:"Test"}); 
}

the code crashes - it adds more element to an array and the loop is going endless

"the code crashes" with which error? Modifying the array while iterating over it usually causes problems (unless done right). — Felix Kling
– Felix Kling, Commented Jan 11, 2018 at 10:27

gurvinder372 · Accepted Answer · 2018-01-11 10:34:57Z

1

the code crashes - it adds more element to an array and the loop is going endless

Because index < results[1].length never fails as you keep on increasing the length of result by adding elements to it.

make it

var length = results[1].length;
for (index = 0; index < length; ++index) {
    results[1].splice( index, 0, {Keys:"Test"} ); 
}

Also, this will keep pointing the index to the newly added item, so increase the index as well

for (index = 0; index < results[1].length; index = index + 2) 
{
    results[1].splice( index, 0, {Keys:"Test"} ); 
}

answered Jan 11, 2018 at 10:27

gurvinder372

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7 Comments

This will not iterate over the last N element where N is the number of newly inserted item, isn't it?

The second one will not iterate over all original elements either.

OP hasn't mentioned about iterate over last N element. What did I missed?

@gurvinder372: That would require to update length as well. Or keep index < results[1].length;.

@FelixKling Yes, I missed that part. Thanks for pointing it out.

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