Description and example usage of javascript synchronous callback

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Description

1. The synchronous callback is executed during the execution of the high-order function of the callback.

2. The synchronous callback is blocked: the high-order function cannot complete its execution until the callback is completed.

Greet () is a synchronous callback function because it executes concurrently with the higher-order function map ().

Example

Function map (array, callback) {console.log ('map () start'); const mappedArray = []; for (const item of array) {mappedArray.push (callback (item))} console.log ('map () complete'); return mappedArray;} function greet (name) {console.log ('greet () called'); return `Hello, ${name}! `;} const persons = ['Mini']; map (persons, greet) / / map () starts / / greet () is called / / map () is finished, and the study of "instructions and instance usage of javascript synchronous callback" is over. I hope to solve everyone's doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!