JavaScript from "complex" to "Jane" to do the array to weight

As JavaScript provides more syntax, there are more and more ways to re-weigh arrays. Now from the most primitive way to the most concise way, step by step to analyze.

Double loop

The array de-weight, is not the comparison of array elements, to remove the repetition. The most primitive way is not the double cycle of comparison processing.

Creates an array of res to hold the returned result; the outer loop iterates through each of the array elements in target, and the inner loop compares the element in target with each value in the Res array, and if it is not the same, it is stored in the Res. The loop is finished, returning the array after the redo. This primitive approach has good compatibility.

IndexOf optimization of inner-layer loops

Use indexof to optimize the inner loop in this chestnut. The IndexOf () method returns the first index in the array where a given element can be found, or 1 if it does not exist.

Using the IndexOf method, there is no need for an inner loop, and there are other ways to optimize the inner loop.

JavaScript Learning Group: 453833554

Object key-value pairs optimize inner-layer loops

object's keys are duplicated, and this feature can be used to judge the repetition of the elements

NOTE: Because the keys of the object are characters, it is not possible to distinguish between 1 and ' 1 ', so you need to make a change, and then add the type judgment.

With the type judgment, 1 corresponds to Number1, ' 1 ' corresponds to String1, and can be separated by normal area.

Filter to optimize the outer loop

Use filter in this chestnut to optimize the outer loop. The filter () method creates a new array that contains all the elements of the test implemented by the provided function.

Filtering directly on target, returns True if the element first appears, or false, so that each element in the newly created array will only appear once for the purpose of de-weight. At this point we no longer use the For loop, and the amount of code is much reduced.

Set de-weight

ES6 provides a new Set of data structures. It is similar to an array, but the values of the members are unique and have no duplicate values. This feature is used to get the array to be heavy and convenient.

‘...‘ is an extension operator in ES6, where the function is to expand the set into a comma-separated sequence of arguments, and it is very simple to implement an array de-weight. Children who are unfamiliar with the ES6 Grammar are aware of their own first. If you use the arrow function again, it is really a sentence to be done, as follows:

At this point, a line from the more than 10-line code of the double loop to the last set+ arrow function is done. From ' Complex ' to ' Jane ' have realized the weight of the array, the code is reduced behind the application of the JavaScript method. In fact, the core ideas have not changed, the means of implementation has changed.

JavaScript Learning Group: 453833554

JavaScript from "complex" to "Jane" to do the array to weight