In Javascript, How Do I Check If An Array Has Duplicate Multiple Values?

I'm sorry I can't speak English well. These are my simple code with a few parameters array: if (link.indexOf({'x' : '1' , 'y':'2' , 'z': '3'}) === -1) { link.push({

Solution 1:

You can create a separate function for this to check if element exists in list or not.

Try this:

functiondoesExistInList(list, obj) {
  for (let i = 0; i < list.length; i++) {
    if (list[i].x === obj.x && list[i].y === obj.y && list[i].z === obj.z) {
      returntrue;
    }
  }
  returnfalse;
}

let link = [];
let obj = { "x": "1", "y": "2", "z": "3" };
if (doesExistInList(link, obj) == false) {
  link.push(obj);//insert same object to list
} else {
  alert("Duplicate");
}
console.log(link);

Solution 2:

JavaScript compares objects by reference -- that is, do the two objects point to the exact same spot in memory?

If so, then not only are they equal -- but they are the exact same object.

What you want is a compare-by-value -- and you'll have to do that yourself.

(You could also use the find method, but that isn't quite as supported.)

const link = [];

const testVal = {
  "x": "1",
  "y": "2",
  "z": "3"
};

const results = link.filter(k =>
  k.x === testVal.x &&
  k.y === testVal.y &&
  k.z === testVal.z);


if (results.length === 0) {
  link.push(testVal);
} else {
  alert("Duplicate");
}

console.log(link);

Solution 3:

If two objects have same keys and same values in javascript they are different objects. To compare two objects you need to create separate function. Then use some() to compare each object in array with given object

Note: The below doesn't work for nested object. But it will work for your given case

functioncompareObjs(a, b){
  if(Object.keys(a).length === Object.keys(b).length){
    for(let k in a){
      if(a[k] !== b[k]){
        returnfalse;
      }
    }
  }
  else{
    returnfalse;
  }
  returntrue;
}

const obj = {
      "x": "1",
      "y": "2",
      "z": "3"
   }

if(!link.some(a =>compareObjs(obj, a))) {
   link.push(obj);
} else {
   alert("Duplicate");
}

Solution 4:

There are couple of options to do that. The issue is with your code even if it looks like you are trying to check with indexOf if the array contains the targeted object. The main issue is it does not check the values of the properties but the reference of the original object.

So the first solution is, checking each property of the object in a hard coded way if you have the same structure for your object:

const links = [
   {x: '2', y: '3', z: '1'},
   {x: '11', y: '32', z: '73'},
   {x: '1', y: '2', z: '3'},
   {x: '93', y: '6', z: '76'},
];

const aim = {x: '1', y: '2', z: '3'};

links.forEach(link => {
  const result = link.x === aim.x && link.y === aim.y && link.z === aim.z;  
  console.log(link, `This object has same property values as aim: ${result}`);
});

There are smarter solutions, just like getting the keys of the object what it has dynamically and comparing them by using some():

const links = [
   {x: '2', y: '3', z: '1'},
   {x: '11', y: '32', z: '73'},
   {x: '1', y: '2', z: '3'},
   {x: '93', y: '6', z: '76'},
];

const aim = {x: '1', y: '2', z: '3'};

links.forEach(link => {
  const keysOfLink = Object.keys(link);
  const keysOfAim = Object.keys(aim);
  const result = keysOfLink.length === keysOfAim.length &&
                 keysOfLink.some(key => link[key] === aim[key]);
  console.log(link, `This object has same property values as aim: ${result}`);
});

I would go with the second option, that's definitely smartest way to check.

From Array.prototype.some()'s documentation:

The some() method tests whether at least one element in the array passes the test implemented by the provided function. It returns a Boolean value.

Once in the result variable you have true value, you can push as you wanted originally.

I hope this helps!