Deduplication of Java Array

Scenario 1 of directory array deduplication, ES6-set2, deduplication using Map data structure 3, nested loop + splice4, forEach + indexOf summary

Scenario of array deduplication

Set the array var arr =[1,1,‘true',‘true',true,true,66,66,false,false,undefined,undefined, null,null, NaN, NaN, 0, 0, ‘a', ‘a',{},{}] Filter out duplicate values in

1. ES6-set

Using set in ES6 is the easiest way to remove duplicate

<script>
   var arr=[1,2,3,4,1,2,3]
   // First, convert the array to set
   var set=new Set(arr) 
   // Again set Convert to an array 
   console.log(Array.from(set))
</script>

2. Using Map data structure to remove duplicate

Create an empty Map data structure, traverse the array that needs to be deduplicated, and store every element of the array as key into Map. Since the same key value will not appear in Map, the final result is the de-duplication result

function shuzu(arr) {
  let map = new Map();
  let array = new Array();  //  Arrays are used to return results 
  for (let i = 0; i < arr.length; i++) {
    if(map .has(arr[i])) {  //  If there is a key Value 
      map .set(arr[i], true);
    } else {
      map .set(arr[i], false);   //  If there is no such thing as key Value 
      array .push(arr[i]);
    }
  }
  return array ;
}

3. Nested Loop + splice

function shuzu(arr){
for(var i = 0 ; i < arr.length; i++){
for( var j = i + 1; j < arr.length; j++){
if( arr[i] === arr[j] ){
arr.splice(j,1);
}
}
}
return arr;
}

4. forEach + indexOf

function shuzu(arr){
var res = [];
arr.forEach((val,index)=>{
if( res.indexOf(val) === -1 ){
res.push(val);
}
});
return res;
}

Summarize

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