Facebook Interview: Filter Properties

solution.js

function createExcludedMap(excludes) {
  return excludes.reduce((map, pair) => {
    const values = map.get(pair.k);

    if (values) {
      values.push(pair.v);
      return map.set(pair.k, values);
    }

    return map.set(pair.k, [pair.v]);
  }, new Map()); 
}

/*
function excludeItems(items, excludes) {
  excludes.forEach((pair, outer) => {
    items = items.filter((item, inner)  => { 
      return item[pair.k] !== pair.v;
    });
    
  });

  return items;
}
*/


/*
function excludeItems(items, excludes) {
  const included = [];
 
  for (const item of items) {
    let excluded = false;
    
    for (const [key, values] of excludesMap) {
      if (item[key] && values.includes(item[key])) {
         excluded = true;
         break;
      }
    }
    
    if (!excluded) {
      included.push(item);
    }
  }
  
  return included; 
}
*/

function excludeItems(items, excludes) {
  for (const item of items) {
    for (const [key, values] of excludesMap) {
      items = items.filter((item) => !values.includes(item[key]));
    }
  }
  
  return items; 
}


const items = [
  { color: 'red', type: 'tv', age: 18 },
  { color: 'red', type: 'phone', age: 20 },
  { color: 'silver', type: 'tv', age: 18 },
  { color: 'silver', type: 'phone', age: 20 }
];

const excludes = [
  { k: 'color', v: 'red' },
  { k: 'color', v: 'blue' },
  { k: 'type', v: 'phone' },
];

/*
const excludesMap = new Map(
  ['color', ['red', 'blue']],
  ['type', ['phone']]
);
*/
const excludesMap = createExcludedMap(excludes);
console.log('result', excludeItems(items, excludesMap));

Rather than chaining items on an array for excludesMap, you could use an obj with O(1) access

excludesMap {
  'color' => { red: true, blue: true },
  'type' => { phone: true }
}

This is how I did it:

function createExcludedMap(excludes) {
  return excludes.reduce((map, pair) => {
    if (map.has(pair.k)) {
      const prevVal = map.get(pair.k);
      return map.set(pair.k, {
        ...prevVal,
        [pair.v]: true,
      });
    } else return map.set(pair.k, { [pair.v]: true });
  }, new Map());
}

function excludeItems(items, excludes) {
  return items.filter((item) => {
    for (prop in item) {
      if (excludes.has(prop) && excludes.get(prop)[item[prop]]) return false;
    }
    return true;
  });
}

Breaking down:

excludes.get(prop)[item[prop]]

In the 1st iteration, you get:

prop // 'color'
excludes.get(prop) //  { blue: true, red: true}
item[prop] // current item's property value, i.e., 'red'