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60 lines
2.0 KiB
JavaScript
60 lines
2.0 KiB
JavaScript
var createAggregator = require('../internal/createAggregator');
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/** Used for native method references. */
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var objectProto = Object.prototype;
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/** Used to check objects for own properties. */
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var hasOwnProperty = objectProto.hasOwnProperty;
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/**
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* Creates an object composed of keys generated from the results of running
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* each element of `collection` through `iteratee`. The corresponding value
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* of each key is an array of the elements responsible for generating the key.
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* The `iteratee` is bound to `thisArg` and invoked with three arguments:
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* (value, index|key, collection).
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*
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* If a property name is provided for `iteratee` the created `_.property`
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* style callback returns the property value of the given element.
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*
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* If a value is also provided for `thisArg` the created `_.matchesProperty`
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* style callback returns `true` for elements that have a matching property
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* value, else `false`.
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*
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* If an object is provided for `iteratee` the created `_.matches` style
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* callback returns `true` for elements that have the properties of the given
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* object, else `false`.
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*
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* @static
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* @memberOf _
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* @category Collection
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* @param {Array|Object|string} collection The collection to iterate over.
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* @param {Function|Object|string} [iteratee=_.identity] The function invoked
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* per iteration.
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* @param {*} [thisArg] The `this` binding of `iteratee`.
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* @returns {Object} Returns the composed aggregate object.
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* @example
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*
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* _.groupBy([4.2, 6.1, 6.4], function(n) {
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* return Math.floor(n);
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* });
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* // => { '4': [4.2], '6': [6.1, 6.4] }
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*
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* _.groupBy([4.2, 6.1, 6.4], function(n) {
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* return this.floor(n);
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* }, Math);
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* // => { '4': [4.2], '6': [6.1, 6.4] }
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*
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* // using the `_.property` callback shorthand
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* _.groupBy(['one', 'two', 'three'], 'length');
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* // => { '3': ['one', 'two'], '5': ['three'] }
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*/
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var groupBy = createAggregator(function(result, value, key) {
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if (hasOwnProperty.call(result, key)) {
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result[key].push(value);
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} else {
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result[key] = [value];
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}
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});
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module.exports = groupBy;
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