Two Arrays Inner Join In Javascript

Following are the 2 arrays I have, var g= [ { id: 36, name: 'AAA', goal: 'yes' }, { id: 40, name: 'BBB', goal: 'yes' }, { id: 39, name: 'JJJ', goal: 'yes'

Solution 1:

Here are some joins for you, take your pick!

function* innerJoin(a, b, key) {
    let idx = newMap(b.map(x => [key(x), x]));
    for (let x of a) {
        let k = key(x);
        if (idx.has(k))
            yield {...x, ...idx.get(k)};
    }
}

function* leftJoin(a, b, key) {
    let idx = newMap(b.map(x => [key(x), x]));
    for (let x of a) {
        let k = key(x);
        yield idx.has(k) ? {...x, ...idx.get(k)} : x;
    }
}

function* rightJoin(a, b, key) {
    let idx = newMap(a.map(x => [key(x), x]));
    for (let x of b) {
        let k = key(x);
        yield idx.has(k) ? {...idx.get(k), ...x} : x;
    }
}


//var A = [
    {id: 1, a: 'a1'},
    {id: 2, a: 'a2'},
    {id: 7, a: 'a3'},
    {id: 8, a: 'a4'}
];

var B = [
    {id: 1, b: 'b1'},
    {id: 2, b: 'b2'},
    {id: 9, b: 'b3'}
];


console.log('INNER:')
console.log(...innerJoin(A, B, x => x.id))
console.log('LEFT')
console.log(...leftJoin(A, B, x => x.id))
console.log('RIGHT')
console.log(...rightJoin(A, B, x => x.id))

Solution 2:

What your expected results asks for is not a left join. You're asking for an inner join of g and c using id and to merge the properties. The below should do this

var g= [ 
        { id: 36, name: 'AAA', goal: 'yes' },
        { id: 40, name: 'BBB', goal: 'yes' },
        { id: 39, name: 'JJJ', goal: 'yes' },
        { id: 27, name: 'CCC', goal: 'yes' }];

var c= [ 
        { id: 36, color:"purple" },
        { id: 40, color:"purple" },
        { id: 100, color:"pink"} ];
    
functionmergeBy(key, dataL, dataR) {
  const rMap = dataR.reduce((m, o) => m.set(o[key], { ...m.get(o[key]), ...o }), newMap);
  
  return dataL.filter(x => rMap.get(x[key])).map(x => ({...x, ...rMap.get(x[key]) }));
}

console.log(mergeBy("id",g, c))

Solution 3:

You could get uncommon keys and filter the merged results with.

constmergeCommon = (a, b, key) => {
        const aByKey = a.reduce((m, o) => m.set(o[key], o), newMap);

        return b.reduce((r, o) => {
            if (aByKey.has(o[key])) r.push({ ... aByKey.get(o[key]), ...o});
            return r;
        }, []);
    },
    g = [{ id: 36, name: 'AAA', goal: 'yes' , 'random': 27 }, { id: 40, name: 'BBB', goal: 'yes' }, { id: 39, name: 'JJJ', goal: 'yes' }, { id: 27, name: 'CCC', goal: 'yes' , lag: "23.3343" }],
    c = [{ id: 36, name: 'AAA', goal: 'yes', color:"purple" }, { id: 40, name: 'BBB', circle: 'yes', color:"purple" }, { id: 100, name: 'JJJ', circle: 'yes'}],
    result = mergeCommon(g, c, 'id');

console.log(result);

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Solution 4:

You can use Maps for joining two arrays. See the code snippet for three types of joins Left Join, Right Join, Inner Join.

All the three joins take O(N) time.

const g = [
  { id: 36, name: 'AAA', goal: 'yes', random: 27 },
  { id: 40, name: 'BBB', goal: 'yes' },
  { id: 39, name: 'JJJ', goal: 'yes' },
  { id: 27, name: 'CCC', goal: 'yes', lag: '23.3343' },
];

const c = [
  { id: 36, name: 'AAA', goal: 'yes', color: 'purple' },
  { id: 40, name: 'BBB', circle: 'yes', color: 'purple' },
  { id: 100, name: 'JJJ', circle: 'yes' },
];

const gMap = newMap(g.map(o => [o.id, o]));
const cMap = newMap(c.map(o => [o.id, o]));

const leftJoin = g.reduce(
  (a, o) => (cMap.has(o.id) ? [...a, { ...o, ...cMap.get(o.id) }] : [...a, o]),
  []
);

const rightJoin = c.reduce(
  (a, o) => (gMap.has(o.id) ? [...a, { ...o, ...gMap.get(o.id) }] : [...a, o]),
  []
);

const innerJoin = g.reduce(
  (a, o) => (cMap.has(o.id) ? [...a, { ...o, ...cMap.get(o.id) }] : a),
  []
);

console.log("LEFT JOIN\n", leftJoin)
console.log("RIGHT JOIN\n", rightJoin)
console.log("INNER JOIN\n", innerJoin)

Solution 5:

var g = [ 
    { id: 36, name: 'AAA', goal: 'yes' , 'random':27},
    { id: 40, name: 'BBB', goal: 'yes' },
    { id: 39, name: 'JJJ', goal: 'yes' },
    { id: 27, name: 'CCC', goal: 'yes' , lag: "23.3343"}
];

var c = [ 
    { id: 36, name: 'AAA', goal: 'yes', color:"purple" },
    { id: 40, name: 'BBB', circle: 'yes', color:"purple" },
    { id: 100, name: 'JJJ', circle: 'yes'} 
];


constcombinedArr = (arr1, arr2) => {
//Filter the arr2 and find the only matching elements from the first arrayconst filteredArr = arr2.filter(({id}) => arr1.some(({id: arr1Id}) => arr1Id === id));
    //Loop through the filtered array and fetch the matching item from first and add obj from filtered arrayreturn filteredArr.map(obj => {
        return {
            ...arr1.find(({id}) => id === obj.id),
            ...obj
        }
    })
}    
console.log(combinedArr(g, c));

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  max-height: 100%!important;
}