git ssb

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'use strict'
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function id (e) { return e }
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var prop = require('../util/prop')
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var filter = require('./filter')
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//drop items you have already seen.
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module.exports = function unique (field, invert) {
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  field = prop(field) || id
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  var seen = {}
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  return filter(function (data) {
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    var key = field(data)
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    if(seen[key]) return !!invert //false, by default
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    else seen[key] = true
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    return !invert //true by default
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  })
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}
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