stdlib - A standard library for javascript and node.js

This tutorial demonstrates how to use stdlib - the standard library for JavaScript and Node.js — by building a simple table with data of different types and performing aggregate operations on the data.

Use Case

Given a list containing details of people, we will construct a table which contains details of people and perform aggregate functions on the data.

Steps

1. Install the stdlib library -

$ npm install @stdlib/stdlib

2. Create a new file - demo.js

3. Import stdlib modules -

var tabulate = require('@stdlib/utils/tabulate');
var countBy = require('@stdlib/utils/count-by');
var groupBy = require('@stdlib/utils/group-by');

4. Define the array -

var people = [
{ name: 'Anand', age: 25, country: 'India' },
{ name: 'Bob', age: 24, country: 'Canada' },
{ name: 'Anita', age: 25, country: 'India' },
{ name: 'David', age: 26, country: 'UK' },
{ name: 'Eve', age: 24, country: 'Canada' },
{ name: 'Frank', age: 30, country: 'UK' },
];

5. Construct a frequency table -

var table = tabulate(people);

/* returns [
  [
    { name: 'Anand', age: 25, country: 'India' },
    1,
    0.16666666666666666
  ],
  [
    { name: 'Bob', age: 32, country: 'Canada' },
    1,
    0.16666666666666666
  ],
  [
    { name: 'Anita', age: 25, country: 'India' },
    1,
    0.16666666666666666
  ],
  [ { name: 'David', age: 40, country: 'UK' }, 1, 0.16666666666666666 ],
  [
    { name: 'Eve', age: 32, country: 'Canada' },
    1,
    0.16666666666666666
  ],
  [ { name: 'Frank', age: 40, country: 'UK' }, 1, 0.16666666666666666 ]
] */

6. Count the age of people -

var ageCounts = countBy(people, person => person.age);

/* returns { '25': 2, '32': 2, '40': 2 } */

7. Group the people by the country -

var groupedByCountry = groupBy(people, person => person.country);

/* returns {
  India: [
    { name: 'Anand', age: 25, country: 'India' },
    { name: 'Anita', age: 25, country: 'India' }
  ],
  Canada: [
    { name: 'Bob', age: 32, country: 'Canada' },
    { name: 'Eve', age: 32, country: 'Canada' }
  ],
  UK: [
    { name: 'David', age: 40, country: 'UK' },
    { name: 'Frank', age: 40, country: 'UK' }
  ]
} */

8. Run your file -

node demo.js

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Command Line Utility

In case you want to run as command-line utility then run -

stdlib repl

Run the given commands in the command line in the same order.