How to remove duplicate property values in array – JavaScript?

Let’s say the following is our array −

var details = [
   {
      studentName: "John",
      studentMarks: [78, 98]
   },
   {
      studentName: "David",
      studentMarks: [87, 87]
   },
   {
      studentName: "Bob",
      studentMarks: [48, 58]
   },
   {
      studentName: "Sam",
      studentMarks: [98, 98]
   },
]

We need to remove the duplicate property value i.e. 87 is repeating above. We need to remove it.

For this, use the concept of map().

Example

Following is the code −

var details = [
   {
      studentName: "John",
      studentMarks: [78, 98]
   },
   {
      studentName: "David",
      studentMarks: [87, 87]
   },
   {
      studentName: "Bob",
      studentMarks: [48, 58]
   },
   {
      studentName: "Sam",
      studentMarks: [98, 98]
   },
]
details.map(tempObj => {
   if (typeof (tempObj.studentMarks) == 'object') {
      tempObj.studentMarks = [... new Set(tempObj.studentMarks)]
      if (tempObj.studentMarks.length == 1) {
         tempObj.studentMarks = tempObj.studentMarks[0]
      }
   }
});
console.log(details);

To run the above program, you need to use the following command −

node fileName.js.

Here, my file name is demo292.js.

Output

This will produce the following output on console −

PS C:\Users\Amit\javascript-code> node demo292.js
[
   { studentName: 'John', studentMarks: [ 78, 98 ] },
   { studentName: 'David', studentMarks: 87 },
   { studentName: 'Bob', studentMarks: [ 48, 58 ] },
   { studentName: 'Sam', studentMarks: 98 }
]