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