Javascript ternary operator syntax not understood

Question

I want to understand this please, someone can write as (if/else/elseif) statments ???

lists[list === 'todo' ? 'done' : 'todo'].appendChild(task);

Thanks

Strange logic – if something has status „todo” add it to „done” otherwise add to „todo” — Krzysztof Safjanowski, May 10 '16 at 20:11
I think ternary operator duplicate is at least a half of the OP's confusion. Mostly it's about combination of bracket notation with ternary. — dfsq, May 10 '16 at 20:19

dfsq · Accepted Answer · 2016-05-10T20:14:48.983

3

You can rewrite it as:

if (list === 'todo') {
    lists.done.appendChild(task);
}
else {
    lists.todo.appendChild(task);
}

The thing here is that you can access any property of the object via bracket notation, which allows variables and expressions resolving to a property name. Thus, lists.done is equivalent to lists['done'] but with the later you can use expressions to calculate key name. This is what you have in the original example.

edited May 10 '16 at 20:14

answered May 10 '16 at 20:09

dfsq

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This works , thank you very much – May 10 '16 at 20:30

score 1 · Answer 2 · answered May 10 '16 at 20:11

1

if (list === 'todo') {
    lists['done'].appendChild(task);
else {
    lists['todo'].appendChild(task);
}

answered May 10 '16 at 20:11

stefanhorne

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Javascript ternary operator syntax not understood

2 Answers2