Comparing two arrays and filtering one array upon this in javascript and react

Question

I am trying to compare two arrays of objects as following :

const obj1 = [
        {name:"Mark"},
        {name:"David"},
        {name:"Ellie"},
        {name:"Zuank"},
        {name:"Philip"},
        {name:"Den"},
    ]
    const obj2 = [
        {name:"Mark"},
        {name:"David"},
        {name:"Zuank"},
        {name:"Philip"},
    ]

I want to check if the name of every object exists in the second object or not. If yes, I want to push that object to a new array with a new property named "Matched" added to each object with a value of "true". Otherwise, the Matched property will be false. This is the final result I want to achieve :

  const res = [
        { name: "Mark", matched: true },
        { name: "David", matched: true },
        { name: "Ellie", matched: false },
        { name: "Zuank", matched: true },
        { name: "Philip", matched: true },
        { name: "Den", matched: false },
    ]

--Edit Here is what I have tried so far guys :

obj1.map((element, index) => {
        if (obj2[index].name === element.name) {
            resArr.push({ name: element.name, matched: true })
        }
        else {
            resArr.push({ name: element.name, matched: false })
        }
    })

Can you show what you have tried so far to solve this problem yourself? — Yousaf
– Yousaf, Commented Aug 27, 2020 at 14:26
obj1.map((element, index) => { if (obj2[index].name === element.name) { resArr.push({ name: element.name, matched: true }) } else { resArr.push({ name: element.name, matched: false }) } }) — Saif
– Saif, Commented Aug 27, 2020 at 14:30

hgb123 · Accepted Answer · 2020-08-27 14:32:33Z

2

You could do a map obj1 with some on obj2 to check if obj1 element is on obj2

const obj1 = [
  { name: "Mark" },
  { name: "David" },
  { name: "Ellie" },
  { name: "Zuank" },
  { name: "Philip" },
  { name: "Den" },
]

const obj2 = [
  { name: "Mark" },
  { name: "David" },
  { name: "Zuank" },
  { name: "Philip" },
]

const res = obj1.map((el1) => ({
  name: el1.name,
  match: obj2.some((el2) => el2.name === el1.name),
}))

console.log(res)

answered Aug 27, 2020 at 14:32

hgb123

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Comments

Ele · Accepted Answer · 2020-08-27 14:32:20Z

2

You can use the function map to build the desired output and the function some to check for a specific object by the property name.

const obj1 = [{name:"Mark"},            {name:"David"},            {name:"Ellie"},            {name:"Zuank"},            {name:"Philip"},            {name:"Den"},        ],
      obj2 = [{name:"Mark"},        {name:"David"},        {name:"Zuank"},        {name:"Philip"},    ],
      result = obj1.map(({name}) => ({name, matched: obj2.some(({name: name2}) => name2 === name)}));

console.log(result);

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

answered Aug 27, 2020 at 14:32

Ele

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Jonas Wilms · Accepted Answer · 2020-08-27 14:41:48Z

1

You could build a set of obj2:

  const names = new Set(obj2.map(it => it.name));

Then mapping obj1 can be done in O(n):

  const result = obj1.map(({ name }) => ({ name, matched: names.has(name) }));

answered Aug 27, 2020 at 14:41

Jonas Wilms

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Comments

Nithish · Accepted Answer · 2020-08-27 14:37:29Z

0

You can make use of Array.map and Array.some.

const obj1 = [{name:'Mark'},{name:'David'},{name:'Ellie'},{name:'Zuank'},{name:'Philip'},{name:'Den'}];

const obj2 = [{name:'Mark'},{name:'David'},{name:'Zuank'},{name:'Philip'}];


const getProcessedResult = (data1, data2) => {
  return data1.map(d1 => ({
    ...d1,
    "matched": data2.some(d2 => d2.name === d1.name)
  }));
}

console.log(getProcessedResult(obj1, obj2))

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

answered Aug 27, 2020 at 14:37

Nithish

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Nina Scholz · Accepted Answer · 2020-08-27 14:42:37Z

0

You could take a Set for all names and map the new property by checking the set.

const
    array1 = [{ name: "Mark" }, { name: "David" }, { name: "Ellie" }, { name: "Zuank" }, { name: "Philip" }, { name: "Den" }],
    array2 = [{ name: "Mark" }, { name: "David" }, { name: "Zuank" }, { name: "Philip" }],
    names = new Set(array2.map(({ name }) => name)),
    result = array1.map(o => ({ ...o, matched: names.has(o.name) }));

console.log(result);

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

answered Aug 27, 2020 at 14:42

Nina Scholz

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Comments

Hayden Tofts · Accepted Answer · 2020-08-27 14:42:51Z

0

Just map through obj1 and while mapping filter obj2 to check if the current name is in obj2. If it is then push the name along with the matched value of true into obj3. If it isn't then push the name along with the matched value of false into obj3.

const obj1 = [
  {name:"Mark"},
  {name:"David"},
  {name:"Ellie"},
  {name:"Zuank"},
  {name:"Philip"},
  {name:"Den"}
]
const obj2 = [
  {name:"Mark"},
  {name:"David"},
  {name:"Zuank"},
  {name:"Philip"}
]
let obj3 = []

obj1.map(function(a) {
 let matched = obj2.filter(b => a.name === b.name);
 if (matched.length) {
  obj3.push({name: a.name, matched: true});
 } else {
  obj3.push({name: a.name, matched: false});
 }
})

console.log(obj3);

answered Aug 27, 2020 at 14:42

Hayden Tofts

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