JavaScript array deduplication algorithm example

This article mainly introduces the JavaScript array deduplication algorithm. It summarizes and analyzes the reading, writing, traversing, comparison, sorting and other operations related to JavaScript array deduplication as well as implementation techniques related to algorithm improvement in the form of examples. Friends in need can refer to the following

The examples in this article summarize the JavaScript array deduplication algorithm. Share it with everyone for your reference, the details are as follows:

Test case: arr = ["1",3,"1",1,4,5,1,"2",5,1,{" name":"li","age":20},2,4,3,{"name":"li","age":20},""];

method 1: With the help of temporary array and indexOf, the algorithm complexity is: O(n^2)

function unique1(arr){
  var temp = [];
  for(var i=0; i<arr.length; i++){
    if(temp.indexOf(arr[i]) == -1){
      temp.push(arr[i]);
    }
  }
  return temp;
}

Test result: unique1(arr): ["1", 3 , 1, 4, 5, "2", Object { name="li", age=20}, 2, Object { name="li", age=20}, ""]

bug Unable Differentiate objects

Method 2: Use the Object object in JavaScript as a hash table

function unique2(arr){
  var temp=[];
  var hash={};
  for(var i=0; i<arr.length;i++){
    if(!hash[arr[i]]){
      hash[arr[i]]=true;
      temp.push(arr[i]);
    }
  }
  return temp;
}

Test result: unique2(arr): ["1", 3 , 4, 5, "2", Object { name="li", age=20}, ""]

bug: Unable to distinguish: 1 and "1"

Modify

function unique2(arr){
  var temp=[];
  var hash={};
  for(var i=0; i<arr.length;i++){
      var item = arr[i];
    var key = typeof(item)+item;
    if(!hash[key]){
      hash[key]=true;
      temp.push(arr[i]);
    }
  }
  return temp;
}

Test result: unique2(arr): ["1", 3, 1, 4, 5, "2", Object { name="li", age=20}, 2, ""]

Method 3: First use sort to sort the array, and then use a temporary array to store the last one of the same element. This method can only be used for pure Number type arrays

function unique3(arr){
  arr.sort(function(a,b){
    return a-b;
  });
  var temp = [];
  for(var i=0;i<arr.length;i++){
    if(arr[i] !== arr[i+1]){
      temp.push(arr[i]);
    }
  }
  return temp;
}

Above I compiled it for everyone. I hope it will be helpful to everyone in the future.

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