javascript how to find from two object array ?

Question

i have two array object

 var data=[{m:1},{m:2},{m:3},{m:4},{m:5},{m:6},{m:7},{m:8},{m:9},{m:10},{m:11},{m:12}];
 var file=[{m:1},{m:3}];

i want to get array like [true,false,false,true,false,false,false,false,false,false,false,false]

Note : in this ayyar it will return true if it match with file array object from data array object.

i try indexOf but i cann't work for my result.

Your expected result is wrong, it should be: [true,false,true,false,false,false,false,false,false,false,false,false] — Robby Cornelissen
– Robby Cornelissen, Commented Apr 14, 2017 at 9:11

Robby Cornelissen · Accepted Answer · 2017-04-14 09:09:16Z

5

Using Array.prototype.map() and Array.prototype.some():

 let data = [{m:1},{m:2},{m:3},{m:4},{m:5},{m:6},{m:7},{m:8},{m:9},{m:10},{m:11},{m:12}];
 let file = [{m:1},{m:3}];
 
 let result = data.map(d => file.some(f => f.m === d.m));
 
 console.log(result);

answered Apr 14, 2017 at 9:09

Robby Cornelissen

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Nina Scholz · Accepted Answer · 2017-04-14 09:11:39Z

4

You could use a hash table and map the occurence.

var data = [{ m: 1 }, { m: 2 }, { m: 3 }, { m: 4 }, { m: 5 }, { m: 6 }, { m: 7 }, { m: 8 }, { m: 9 }, { m: 10 }, { m: 11 }, { m: 12 }],
    file = [{ m: 1 }, { m: 3 }],
    hash = Object.create(null),
    result;
    
file.forEach(function (a) {
    hash[a.m] = true;
});

result = data.map(function (a) {
    return hash[a.m] || false;
});

console.log(result);

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

ES6 with Set

var data = [{ m: 1 }, { m: 2 }, { m: 3 }, { m: 4 }, { m: 5 }, { m: 6 }, { m: 7 }, { m: 8 }, { m: 9 }, { m: 10 }, { m: 11 }, { m: 12 }],
    file = [{ m: 1 }, { m: 3 }],
    mySet = new Set(file.map(a => a.m)),
    result = data.map(a => mySet.has(a.m));

console.log(result);

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

answered Apr 14, 2017 at 9:11

Nina Scholz

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1 Comment

Robby Cornelissen Over a year ago

The lookup table/set is bound to be faster than my approach, especially as the list grows longer +1.

S B · Accepted Answer · 2017-04-14 09:33:56Z

1

Try this Demo

var data=[{m:1},{m:2},{m:3},{m:4},{m:5},{m:6},{m:7},{m:8},{m:9},{m:10},{m:11},{m:12}];
 var file=[{m:1},{m:3}];
 var re = [];
 for(var i=0;i<data.length;i++){
 	let r = file.find(function findObj(o) { 
    return o.m === data[i].m;
	})
if(r){
  	re.push(true)
  }else{
  re.push(false)
  }
 }
 console.log(re)

edited Apr 14, 2017 at 9:33

answered Apr 14, 2017 at 9:11

S B

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1 Comment

Abhishek Gurjar Over a year ago

I am not the downvoter, but there is only one true in your answer which is not matched with expected output of OP.

raj peer · Accepted Answer · 2017-04-14 09:24:08Z

0

var data = [{m:1},{m:2},{m:3},{m:4},{m:5},{m:6},{m:7},{m:8},{m:9},{m:10},{m:11},{m:12}];
var file = [{m:1},{m:3}];

var result = [];

function remove_duplicates(data, file) {
    for (var i = 0, len = data.length; i < len; i++) { 
        for (var j = 0, len2 = file.length; j < len2; j++) { 
            if (data[i].m === file[j].m) {
                result.push("true")
            }else{
            result.push("false")
            }
        }
    }
console.log(result)
}

remove_duplicates(data,file);

answered Apr 14, 2017 at 9:24

raj peer

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tanmay · Accepted Answer · 2017-04-14 09:41:39Z

0

Funny how ridiculously small it becomes with ES6.

Here, file.map(val => val.m) would give me an array of numbers. [1, 3] which I use to find whether it includes current object's m prop.

 var data=[{m:1},{m:2},{m:3},{m:4},{m:5},{m:6},{m:7},{m:8},{m:9},{m:10},{m:11},{m:12}];
 var file=[{m:1},{m:3}];
 var selection = file.map(val => val.m)
 
 var arr = data.map(obj => selection.includes(obj.m))
 
 console.log(arr)

edited Apr 14, 2017 at 9:41

answered Apr 14, 2017 at 9:21

tanmay

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4 Comments

Nina Scholz Over a year ago

for each iteration of data, you generate a new array for look up.

tanmay Over a year ago

@NinaScholz maybe I should create it first and then use it inside?

Nina Scholz Over a year ago

or a set, like in my answer.

tanmay Over a year ago

@NinaScholz okay, got it, +1, but how would one learn/know which one would be faster approach? how do you go for it?

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