An example description of Node.js missing context this

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1. Missing context (this) means that the function call ends with the wrong value. Losing context is a common problem with conversion functions.

Class MyClass {myCallbackFn (cb) {cb (null, this)} const obj = new MyClass () const promisified = require ('util') .promisify (obj.myCallbackFn) const context = await promisified () console.log (context) / / print undefined instead of MyClass instance!

2. This any object that contains the properties of the function when it is called.

Therefore, you can preserve the context by setting the promisified function to a property of the same object:

Class MyClass {myCallbackFn (cb) {cb (null, this)} const obj = new MyClass () / / preserves the context, because promisified is the attribute of obj obj.promisified = require ('util') .promisify (obj.myCallbackFn) const context = await obj.promisified () console.log (context = obj) / / true Thank you for reading. This is the content of the example of Node.js missing context this. After the study of this article, I believe that we have a deeper understanding of this problem with the example of Node.js losing context this, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!