@emartech/data-aggregator-language

Execute aggregation expressions on a given data set.

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@emartech/data-aggregator-language
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Readme

Data Aggregator Language

Execute aggregation expressions on a given data set.

What it Does

Given the following input data structure,

const input = [{
  date: '2017-09-16',
  reservations: {
    silver: 12,
    gold: 5
  },
  customers: ['brad']
}, {
  date: '2017-09-17',
  reservations: {
    silver: 3,
    gold: 2
  },
  customers: ['angelina']
}]

the parser allows mixing aggregation expressions over the input with common arithmetic operators.

For example,

  • an aggregation expression: SUM reservations.silver would yield 12 + 3 = 15.
  • an aggregation expression mixed with arithmetic: SUM reservations.silver + 3 would yield (12 + 3) + 3 = 18

    Usage

    const aggregator = require('@emartech/data-aggregator-language')(input);
    const result = aggregator('SUM reservations.silver')
    

Supported Syntax in Aggregation Expressions

Examples below are for the input defined above.

Number Results

Constants

  • LENGTH
    • LENGTH (yields 2)
    • LENGTH + 3 (yields 5)
  • Any number literal
    • 5 (yields 5)

Unary Operators

  • SUM
    • SUM reservations.silver (yields 15)
  • LAST
    • LAST reservations.silver (yields 3)
  • AVERAGE
    • AVERAGE reservations.silver (yields 7.5)

Binary Operators

+, -, *, / For example, (LAST reservations.silver + 3) * 2 / 2 (yields 6)

Array Results

  • UNION
    • UNION customers (yields ['brad', 'angelina'])

Boolean Results

  • EMPTY
    • EMPTY UNION customers (yields false)
  • NOT
    • NOT EMPTY UNION customers (yields true)

Using with Webpack

Because of the way the underlying Chevrotain library is implemented, name mangling interferes with the parser's operation. To resolve this issue, webpacked host projects need to disable name mangling for the token names used in this grammar.

To help with this, the module exports these names in a tokens array.

To configure webpack, include the following in your webpack.config.js:

const { tokens } = require('@emartech/data-aggregator-language');


module.exports.optimization = {
    minimizer: [
      new UglifyJsPlugin({
        uglifyOptions: {
          mangle: {
            reserved: tokens
          }
        }
      })
    ]
  };

Commit Convention

Semantic release depends on the Angular commit message conventions. Please follow these.

Credit

Uses SAP/chevrotain for parsing.

If you find any bugs or have a feature request, please open an issue on github!

The npm package download data comes from npm's download counts api and package details come from npms.io.