javascript does not repeat in array

Javascript is a commonly used scripting language, which is widely used in the field of web development. Arrays are one of the most important data types in Javascript. In development, we may need to deduplicate the array to process the data more efficiently. This article will introduce how to remove duplicate elements from an array in Javascript.

1. Using the Set object

The Set object in Javascript is a collection data structure that can store a unique set of values. We can use the Set object to remove duplicate elements from the array. The specific code is as follows:

let arr = [1, 2, 3, 3, 4, 4, 5];
let uniqueArr = [...new Set(arr)];
console.log(uniqueArr); //[1, 2, 3, 4, 5]

Here we first define an array containing duplicate elements arr, and then use new Set( arr)Create a Set object and convert it into an array through the spread operator....

2. Use Array.prototype.reduce() method

Another way to remove duplicates is to use the reduce() method. The reduce() method applies a function to each element of the array and summarizes its results into a single value. In deduplication operation, we can store each element as a key in an object and skip duplicate elements accordingly. The specific code is as follows:

let arr = [1, 2, 3, 3, 4, 4, 5];
let uniqueArr = arr.reduce(function(acc, current) {
  if (acc.indexOf(current) === -1) {
    acc.push(current);
  }
  return acc;
}, []);
console.log(uniqueArr); //[1, 2, 3, 4, 5]

Here we use the reduce() method to traverse each element in the array arr, acc represents the cumulative value, and current represents the current element. In each iteration, we check if the current element is already present in the acc array and push it into the array if not.

3. Use Array.prototype.filter() method

Another way to remove duplicates is to use the filter() method. The filter() method can filter the elements in the array based on a certain condition. In the deduplication operation, we can filter the elements in the array according to a custom condition to remove duplicate elements. The specific code is as follows:

let arr = [1, 2, 3, 3, 4, 4, 5];
let uniqueArr = arr.filter(function(item, index) {
  return arr.indexOf(item) === index;
});
console.log(uniqueArr); //[1, 2, 3, 4, 5]

Here we use the filter() method to check each element in the array. If the element appears at the first position in the array, it will be retained.

To sum up, Javascript provides a variety of methods to remove duplicate elements from an array. Developers can choose different methods to implement this operation based on project requirements. But it should be noted that when dealing with large arrays, using some methods may cause performance problems, so we need to choose carefully.

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