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- # `sum()`
-
- The sum method returns the sum of all items in the collection:
-
- ```js
- collect([1, 2, 3]).sum();
-
- // 6
- ```
-
- If the collection contains nested arrays or objects, you should pass a key to use for determining which values to sum:
-
- ```js
- const collection = collect([
- { name: 'My story', pages: 176 },
- { name: 'Fantastic Beasts and Where to Find Them', pages: 1096 },
- ]);
-
- collection.sum('pages');
-
- // 1272
- ```
-
- In addition, you may pass your own callback to determine which values of the collection to sum:
-
- ```js
- const collection = collect([
- { name: 'Desk', colors: ['Black', 'Mahogany'] },
- { name: 'Chair', colors: ['Black'] },
- { name: 'Bookcase', colors: ['Red', 'Beige', 'Brown'] },
- ]);
-
- const total = collection.sum(product => product.colors.length);
-
- // 6
- ```
-
- [View source on GitHub](https://github.com/ecrmnn/collect.js/blob/master/src/methods/sum.js)
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