Projection/JavaScript/b-disp-opt.js at master · HowProgrammingWorks/Projection · GitHub

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'use strict';

// Projection

const id = (x) => x;

const projection = (meta) => (src) => meta.reduce(

(dest, [name, fn = id, field = name]) =>

(dest[name] = fn(src[field]), dest), {}

);

// Display

const max = (items) => Math.max(...items);

const maxProp = (key) => (items) => max(items.map((x) => x[key]));

const maxLength = maxProp('length');

const col = (name, data) => data.map((obj) => obj[name].toString());

const render = (meta) => (src) => {

const keys = meta.map(([name]) => name);

const maxWidth = keys.map((key) => maxLength(col(key, src)));

const dest = src.map((obj) => maxWidth.map(

(width, i) => obj[keys[i]].toString().padEnd(width + 4)

));

return dest.map((row) => row.join('')).join('\n');

};

// Dataset

const persons = [

{ name: 'Marcus Aurelius', city: 'Rome', born: 121 },

{ name: 'Victor Glushkov', city: 'Rostov on Don', born: 1923 },

{ name: 'Ibn Arabi', city: 'Murcia', born: 1165 },

{ name: 'Mao Zedong', city: 'Shaoshan', born: 1893 },

{ name: 'Rene Descartes', city: 'La Haye en Touraine', born: 1596 },

];

// Metadata

const year = (date) => date.getFullYear();

const diff = (y) => year(new Date()) - year(new Date(y.toString()));

const upper = (s) => s.toUpperCase();

const md = [

['name'],

['place', upper, 'city'],

['age', diff, 'born'],

];

// Usage

const pf = projection(md);

const data = persons.map(pf);

const renderer = render(md);

const res = renderer(data);

console.log(`\n${res}\n`);

Projection/JavaScript/b-disp-opt.js at master · HowProgrammingWorks/Projection · GitHub

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