1 | var baseIteratee = require('./_baseIteratee'),
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2 | baseSum = require('./_baseSum');
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3 |
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4 | /**
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5 | * This method is like `_.sum` except that it accepts `iteratee` which is
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6 | * invoked for each element in `array` to generate the value to be summed.
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7 | * The iteratee is invoked with one argument: (value).
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8 | *
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9 | * @static
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10 | * @memberOf _
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11 | * @since 4.0.0
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12 | * @category Math
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13 | * @param {Array} array The array to iterate over.
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14 | * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
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15 | * @returns {number} Returns the sum.
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16 | * @example
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17 | *
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18 | * var objects = [{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }];
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19 | *
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20 | * _.sumBy(objects, function(o) { return o.n; });
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21 | * // => 20
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22 | *
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23 | * // The `_.property` iteratee shorthand.
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24 | * _.sumBy(objects, 'n');
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25 | * // => 20
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26 | */
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27 | function sumBy(array, iteratee) {
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28 | return (array && array.length)
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29 | ? baseSum(array, baseIteratee(iteratee, 2))
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30 | : 0;
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31 | }
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32 |
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33 | module.exports = sumBy;
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