How to implement array deduplication algorithm in JS

This time I will show you how to implement the array deduplication algorithm in JS. What are the precautions for implementing the array deduplication algorithm in JS? The following is a practical case, let's take a look.

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 to distinguish objects

Method 2: Use Object object in JavaScript as Ha Greek 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"

Modification

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;
}

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!

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