Native javascript - merge two arrays of objects

Question

I want to merge two array like :

arr1 = [
    ['01/09',1],
    ['02/09',2],
    ['03/09',3],
    ['04/09',4]
];

arr2 = [
    ['01/09',13],
    ['03/09',14],
    ['04/09',15],
    ['05/09',16]
];

I want an output like this :

res = [
    ['01/09',1,13],
    ['02/09',2,0],
    ['03/09',3,14],
    ['04/09',4,15],
    ['05/09',0,16]
]

I really want some solutions! Thank you

Answer 1

You could use a combined approach to build the empty array with the parameters adn iterate and build a hash table for the matched items. Then apply the value.

 function merge(arrays) { var hash = Object.create(null), merged = []; arrays.forEach(function (a, i) { a.forEach(function (b) { if (!hash[b[0]]) { hash[b[0]] = Array.apply(null, { length: arrays.length + 1 }).map(function () { return 0 }); hash[b[0]][0] = b[0]; merged.push(hash[b[0]]); } hash[b[0]][i + 1] = b[1]; }); }); return merged; } var arr1 = [['01/09', 1], ['02/09', 2], ['03/09', 3], ['04/09', 4]], arr2 = [['01/09', 13], ['03/09', 14], ['04/09', 15], ['05/09', 16]]; console.log(merge([arr1, arr2]));

 .as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 2

You can use Array.find to search in array and then use Array.concat to merge them.

Array.find + array.concat

 var arr1 = [ ['01/09', 1], ['02/09', 2], ['03/09', 3], ['04/09', 4] ]; var arr2 = [ ['01/09', 13], ['03/09', 14], ['04/09', 15], ['05/09', 16] ]; var result = arr1.map(function(a1) { var _tmp = arr2.find(x => x[0] === a1[0]) || []; return a1.concat(_tmp.splice(1)); }); console.log(result)

Though, I would suggest you to use following structure as it would be more scalable.

Map object

 var arr1 = [ ['01/09', 1], ['02/09', 2], ['03/09', 3], ['04/09', 4] ]; var arr2 = [ ['01/09', 13], ['03/09', 14], ['04/09', 15], ['05/09', 16] ]; var result = {}; arr1.forEach(function(item) { result[item[0]] = item.slice(1) || []; }); arr2.forEach(function(item) { result[item[0]] = result[item[0]] || []; result[item[0]] = result[item[0]].concat(item.slice(1)) }); console.log(result)

Few pointers,

• array.concat will return merged string but will not update the variable. So don't forget to assign it.
• array.find has compatibility issues. Do check them before using it. You can also use array.filter as an alternative.

Answer 3

 var arr1 = [ ['01/09', 1], ['02/09', 2], ['03/09', 3], ['04/09', 4] ]; var arr2 = [ ['01/09', 13], ['03/09', 14], ['04/09', 15], ['05/09', 16] ]; var arr3 = [ ['01/09', 130], ['03/09', 140], ['04/09', 150], ['05/09', 160] ]; function mergeArrays() { var resultObj = {}, resultArray = []; var array = Array.prototype.concat.apply([], Array.prototype.slice.call(arguments)); array.map(function(item) { var key = item[0]; if (!this[key]) { this[key] = []; this[key].push(key); } this[key].push(item[1]); }, resultObj); for (var key in resultObj) { resultArray.push(resultObj[key]); } return resultArray; } console.log(mergeArrays(arr1, arr2, arr3));

Answer 4

You could do this with reduce() and forEach()

 var arr1 = [ ['01/09', 1], ['02/09', 2], ['03/09', 3], ['04/09', 4] ]; var arr2 = [ ['01/09', 13], ['03/09', 14], ['04/09', 15], ['05/09', 16] ]; var obj = {} var result = arr1.reduce(function(r, e) { arr2.forEach(function(el, i) { if (!obj[e[0]]) { obj[e[0]] = [e[0], 0, 0]; r.push(obj[e[0]]); } obj[e[0]][1] = e[1]; if (el[0] == e[0]) { obj[e[0]][2] = el[1]; } else { if (!obj[el[0]]) { obj[el[0]] = [el[0], 0, el[1]]; r.push(obj[el[0]]); } } }) return r; }, []); console.log(result)