Find next todo ID correctly. Fixes #524 #529
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gaearon
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Aug 15, 2015
Find next todo ID correctly. Fixes #524
| @@ -79,7 +79,7 @@ export default function todos(state = initialState, action) { | |||
| switch (action.type) { | |||
| case ADD_TODO: | |||
| return [{ | |||
| id: state.length, | |||
| id: state.reduce((maxId, todo) => Math.max(todo.id, maxId), -1) + 1, | |||
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When maxId is not declared then it should have the value as undefined
however its getting the value as null ?
console output:
Math.max(0, undefined)
NaN
Math.max(0, null)
0
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Initially maxId comes from the seed argument to the reduce(fn, seed). In this case the seed is -1. Then, inside the reduce callback, we return another number if it’s bigger. This is how we get the maximum number. Then we just increment it.
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