How to perform List type conversion in javascript

With the rapid development of JavaScript, more and more developers are beginning to use it to develop various applications and websites. Among them, operating list (List) is an essential task for many JavaScript developers. When using JavaScript for list operations, dealing with type conversion is a frequently encountered problem. In this article, I will introduce the concept and examples of List type conversion to help developers better understand and master it.

Concept

In JavaScript, the List type is usually used to store a set of related values. For example, store a list of student names, store a list of products, etc. The List type has multiple representation methods in JavaScript, the most common of which is array (Array). An array is a sequence composed of several elements. You can access, add, and delete elements in the list through subscripts. For example, you can use the following method to create an array of length 3:

let myArray = new Array(3);

The above code creates an array containing 3 elements, but each element in this array is undefined. Therefore, it is necessary to initialize the array and add relevant values:

myArray[0] = "张三";
myArray[1] = "李四";
myArray[2] = "王五";

Now, the myArray array contains three string elements, namely "Zhang San", "Li Si" and "Wang Wu".

Type conversion

In JavaScript, the List type often requires type conversion to adapt to the needs of different scenarios. For example, type conversion is required when elements in an array need to be concatenated together to form a string. The following are common List type conversions:

Convert array to string

You can use the join() method to convert an array into a string. The join() method can join the array elements in sequence and return a new string. For example:

myArray.join(','); // 返回 "张三, 李四, 王五"

Convert a string into an array

You can use the split() method to convert a string into an array. The split() method splits the string into multiple elements according to the specified delimiter and returns a new array. For example:

let myString = "张三, 李四, 王五";
let myArray = myString.split(", ");

The above code divides the myString string according to the "," delimiter and returns an array myArray containing three elements, namely: "Zhang San", "Li Si" and "Wang Wu" ".

Convert array to object

You can use the reduce() method to convert an array into an object. The reduce() method iterates through each element in the array and aggregates it into a new object. For example:

let myArray = ["张三", "李四", "王五"];
let myObject = myArray.reduce(function(result, item, index) {
  result[index] = item;
  return result;
}, {});

The above code adds each element in the myArray array as an attribute value to a new object and returns this new object myObject.

Convert object to array

You can use the Object.keys() method to convert all property names of an object into an array. For example:

let myObject = {0: "张三", 1: "李四", 2: "王五"};
let myArray = Object.keys(myObject).map(function(key) {
  return myObject[key];
});

The above code converts the property name of the myObject object into an array containing three elements: "0", "1" and "2", and then uses the map() method to traverse the array and return the property value . Finally, the myArray array contains three elements: "Zhang San", "Li Si" and "王五".

Conclusion

This article introduces the concept and examples of List type conversion, mainly introducing the type conversion methods between arrays and strings, arrays and objects, and objects and arrays. In actual development, type conversion is a common task. Developers must understand the relevant knowledge of List type conversion in order to complete development tasks more efficiently.

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