JS array de duplication (including simple array de duplication and object array de duplication)

Simple array de duplication

Simple array ： An array of basic data type elements , Such as [1,‘ Hello ’,true]

Mode one ： utilize Set duplicate removal

utilize Set The feature implementation of automatic de duplication of data structures

let oldList = [1, 2, 3, 3];
let newList = Array.from(new Set(oldList)); //  obtain  [1, 2, 3]

Similar writing is as follows ：

function arrDistinct(arr){
    
    const newArr = new Set(arr);
    return [...newArr]
}

let list = [1,2,2,3,4,4]
console.log(arrDistinct(list))

Mode two ： Nested loop , Compare yourself with yourself , If there is any repetition, delete

let arr = [1, 2, 3, 2, 2, 1, 3, 4, 2, 5];

// Remove duplicate numbers from the array 
for (let i = 0; i < arr.length; i++) {
    
  /* Get all elements after the current element */
  for (let j = i + 1; j < arr.length; j++) {
    
    // Determine whether the values of two elements are equal 
    if (arr[i] == arr[j]) {
    
      // If equal, it proves that there are duplicate elements , Delete j Corresponding elements 
      arr.splice(j, 1);
      // When you delete the current j After the element , The following elements will be filled automatically 
      // send j Self reduction , Compare again j The element of the location 
      j--;
    }
  }
}

console.log(arr); //  The result is  [ 1, 2, 3, 4, 5 ]

Mode three ： Put the non repeating elements into the new array

// Ideas ： Create a new array , Loop traversal , As long as the new array has the value of the old array , There's no need to add .
function arrDistinct(array) {
    
  let newArr = [];
  for (let i = 0; i < array.length; i++) {
    
    // Opening and closing principle 
    let bool = true;
    // Every time you have to judge whether there are values in the old array in the new array .
    for (let j = 0; j < newArr.length; j++) {
    
      if (array[i] === newArr[j]) {
    
        bool = false;
      }
    }
    if (bool) {
    
      newArr[newArr.length] = array[i];
    }
  }
  return newArr;
}

let oldList = [1, 2, 3, 4, 5, 2, 3, 4];

let newList = arrDistinct(oldList);

console.log(newList); //  result  [ 1, 2, 3, 4, 5 ]

Mode 4 ： Use lodash Of uniq()

_.uniq([2, 1, 2]);  // => [2, 1]

Object array de duplication

An array of objects ： An array of objects

function arrDistinctByProp(arr,prop){
    
    // Return only the first occurrence of , Filter out the repeated ones 
    return arr.filter(function(item,index,self){
    
        return self.findIndex(el=>el[prop]==item[prop])===index
    })
}

let list = [
    {
    
        key:'1',
        name:' Brigitte Lin '
    },
    {
    
        key:'2',
        name:' Zhang Sanfeng '
    },
    {
    
        key:'1',
        name:' Duan Yu '
    },
    {
    
        key:'1',
        name:' Duan Yu '
    }
]
 
// adopt name Attribute de duplication 
console.log(arrDistinctByProp(list,'name'))

Another possibility is easier to understand , It is written as follows ：

function soloArray(array, UID) {
    
  let newArr = [];
  let UIDlist = [];

  array.forEach((item) => {
    
    if (!UIDlist.includes(item[UID])) {
    
      UIDlist.push(item[UID]);
      newArr.push(item);
    }
  });
  return newArr;
}

let oldList = [
  {
    
    ID: 1,
    name: " X.h. ",
    age: 10,
  },
  {
    
    ID: 2,
    name: " Zhang San ",
    age: 20,
  },
  {
    
    ID: 2,
    name: " Zhang San ",
    age: 20,
  },
  {
    
    ID: 3,
    name: " Li Si ",
    age: 30,
  },
];

let newList = soloArray(oldList, "ID");
console.log(newList);