31 lines
1.0 KiB
Markdown
31 lines
1.0 KiB
Markdown
### toHash
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Reduces a given Array-like into a value hash (keyed data store).
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Given an Iterable or Array-like structure, call `Array.prototype.reduce.call()` on the provided object to step over it and return an Object, keyed by the reference value.
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```js
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const toHash = (object, key) =>
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Array.prototype.reduce.call(
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object,
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(acc, data, index) => ((acc[!key ? index : data[key]] = data), acc),
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{}
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);
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```
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```js
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toHash([4, 3, 2, 1]); // { 0: 4, 1: 3, 2: 2, 3: 1 }
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toHash([{ a: 'label' }], 'a'); // { label: { a: 'label' } }
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// A more in depth example:
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let users = [{ id: 1, first: 'Jon' }, { id: 2, first: 'Joe' }, { id: 3, first: 'Moe' }];
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let managers = [{ manager: 1, employees: [2, 3] }];
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// We use function here because we want a bindable reference, but a closure referencing the hash would work, too.
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managers.forEach(
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manager =>
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(manager.employees = manager.employees.map(function(id) {
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return this[id];
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}, toHash(users, 'id')))
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);
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managers; // [ { manager:1, employees: [ { id: 2, first: "Joe" }, { id: 3, first: "Moe" } ] } ]
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```
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