68 lines
1.9 KiB
Plaintext
68 lines
1.9 KiB
Plaintext
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{{alias}}( obj, [options,] transform )
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Inverts an object, such that keys become values and values become keys,
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according to a transform function.
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The transform function is provided three arguments:
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- `key`: object key
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- `value`: object value corresponding to `key`
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- `obj`: the input object
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The value returned by a transform function should be a value which can be
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serialized as an object key. Hence, beware when providing objects having
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values which are themselves objects. The function relies on native object
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serialization (`#toString`) when converting transform function return values
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to keys.
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Insertion order is not guaranteed, as object key enumeration is not
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specified according to the ECMAScript specification. In practice, however,
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most engines use insertion order to sort an object's keys, thus allowing for
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deterministic inversion.
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Parameters
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----------
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obj: ObjectLike
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Input object.
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options: Object (optional)
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Options.
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options.duplicates: boolean (optional)
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Boolean indicating whether to store keys mapped to duplicate values in
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arrays. Default: `true`.
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transform: Function
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Transform function.
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Returns
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-------
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out: Object
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Inverted object.
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Examples
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--------
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// Basic usage:
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> function transform( key, value ) { return key + value; };
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> var obj = { 'a': 'beep', 'b': 'boop' };
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> var out = {{alias}}( obj, transform )
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{ 'abeep': 'a', 'bboop': 'b' }
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// Duplicate values:
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> function transform( key, value ) { return value; };
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> obj = { 'a': 'beep', 'b': 'beep' };
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> out = {{alias}}( obj, transform )
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{ 'beep': [ 'a', 'b' ] }
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// Override duplicate values:
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> obj = {};
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> obj.a = 'beep';
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> obj.b = 'boop';
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> obj.c = 'beep';
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> out = {{alias}}( obj, { 'duplicates': false }, transform )
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{ 'beep': 'c', 'boop': 'b' }
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See Also
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--------
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