How to implement JS array deduplication algorithm

This time I will show you how to implement the JS array deduplication algorithm and what are the precautions for implementing the JS array deduplication algorithm. 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!

Recommended reading:

How to operate Angular to implement data requests

How to operate node and use async to control concurrency

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