promise chaining

When looking for how to design a JavaScript API, I found the method chaining this thing, the chain of methods, it seems to be very powerful and interesting, and this is what we used to see in the past. Javascript Method Chaining On Wikipedia, there's this explanation: Copy Code code as follows: Method chaining, also known as named Parameter idiom

receives a parameter value, which represents the result returned by the asynchronous operation, and when the one-step operation succeeds, the user invokes the resolve method, and the actual action is to callbacks actually perform the Callback one by one in the queue is executed; Can be combined with 例1 the code to see, first new Promise , promise the passed function sends an asynchronous request, then

Introduction to Method Chaining in Javascript, javascriptchaining When looking for how to design a Javascript API, I found the Method Chaining. The Method chain seems very powerful and interesting, this is something we often see in the past .. Javascript Method Chaining On Wikipedia, the following explanation is provided:Copy codeThe Code is as follows:Method

？ And! The differenceYou specify optional chaining by placing a question mark ( ? ) after the optional value on which we wish to call a prop Erty, method or subscript if the optional is non- nil . This was very similar to placing a exclamation mark () after a optional value to force the unwrapping of its ! value. The main difference is this optional chaining fails gracefully when nil the optional is, wherea

, and this value returns what is very much fastidious. In the then resolve method, return a new Promise object with the following code: functiontest1 () {varp =NewPromise (function(Resolve, reject) {//do some asynchronous operationsSetTimeout (function() {Console.log (' First promise performed '); Resolve (' The value of the first promise '); }, 200

Examples of Promise asynchronous programming and promise examples The instance is as follows: // 1. solve the asynchronous callback problem // 1.1 how to synchronize asynchronous requests // if there are no pre-and post-order differences between several asynchronous operations, the subsequent tasks can be executed only after multiple asynchronous operations are completed, const fs = require ('fs'); let scho

JavaScript Promise and promise This article focuses on the usage of promise. For a long time, JavaScript processing Asynchronization is based on callback, And the callback mechanism in the front-end development field is almost deeply rooted in the hearts of the people. When designing APIs, browser vendors, SDK developers, and authors of various class libraries ha

Row chain: When a row is too large to fit into any block, row chaining occurs. in this case, the Oracle devide the row into smaller chunks. each Chunk is stored in a block along with the necessary poiters to retrive and assemble the entire row. Row migration: When a row is to be updated and it cannot find the necessary free space in its block, the Oracle will move the entire row into a new block and leave a pointer from the orginal block to the new

Scenario: If varchar and VarChar2 are modified more often, and the modified data length is different each time, this can cause a "row migration" phenomenonConcept:Row chaining and row migration (row migration)When a row of data is too long to be inserted into a single block of data, there are two things that can happen: row chaining or row migration (row migration). When the first time a row is inserted,

The chained invocation pattern allows a method to call an object one after the other. This mode does not consider saving the return value of the function, so the entire invocation can be done in the same line:Myobj.method1 ("Hello"). Method2 (). METHOD3 ("World"). METHOD4 ();If there are methods in the object that do not require a return value, you can let it return the this reference, which makes it easy to continue calling the next method:var obj = { value:1, increment:function () {

Promise of ES6 new features and promise of es6 New Features The promise concept is introduced in the new ES6 to make the callback more elegant. Layer-by-layer nested callback will make javascript less aesthetic and readable. At the same time, javascript also recommends using a chained method to write function calls. So Promis