29 lines
1.1 KiB
Markdown
29 lines
1.1 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( object, ( acc, data, index ) => ( ( acc[ !key ? index : data[ key ] ] = data ), acc ), {} )
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```
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```js
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toHash([ 4,3,2,1 ]); // { 0: 4, 1: 3, 2: 2, 1: 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( manager =>
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manager.employees = manager.employees.map(
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function( id ){
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return this[id];
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},
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toHash( users, 'id' )
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)
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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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