Chained Promises not Passing Rejection
In a promise chain, the resolution of a promise depends on how its error handler functions respond to a rejection. The .then() method returns a new promise for the result of the callback function. If no success or error handler is provided, the result will be passed directly to the next promise.
If the error is handled, the resulting promise will fulfill with the returned value from the error handler. To re-throw the error and propagate it down the chain, throw err instead.
In the widget shop example, when a promise in the chain receives an error, it should throw it onward to ensure that subsequent promises in the chain don't receive a success value.
In a database query chain, if an error occurs in the first query, omitting the error handler will allow the chain to continue, even though the subsequent promises may not receive meaningful values.
db.query({ parent_id: value }).then(function(query_result) {
return db.put({
parent_id: query_result[0].parent_id
});
}).then(function(first_value_result) {
return db.put({
reference_to_first_value_id: first_value_result.id
});
}.then(values_successfully_entered);
In summary, to prevent subsequent promises in a chain from receiving success values after a rejection has occurred, the error handler function should either throw the error or return a rejected promise.
The above is the detailed content of How Do Chained Promises Handle and Propagate Rejections?. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
Which Comment Symbols to Use in JavaScript: A Clear Explanation
Jun 12, 2025 am 10:27 AM
In JavaScript, choosing a single-line comment (//) or a multi-line comment (//) depends on the purpose and project requirements of the comment: 1. Use single-line comments for quick and inline interpretation; 2. Use multi-line comments for detailed documentation; 3. Maintain the consistency of the comment style; 4. Avoid over-annotation; 5. Ensure that the comments are updated synchronously with the code. Choosing the right annotation style can help improve the readability and maintainability of your code.
Java vs. JavaScript: Clearing Up the Confusion
Jun 20, 2025 am 12:27 AM
Java and JavaScript are different programming languages, each suitable for different application scenarios. Java is used for large enterprise and mobile application development, while JavaScript is mainly used for web page development.
Mastering JavaScript Comments: A Comprehensive Guide
Jun 14, 2025 am 12:11 AM
CommentsarecrucialinJavaScriptformaintainingclarityandfosteringcollaboration.1)Theyhelpindebugging,onboarding,andunderstandingcodeevolution.2)Usesingle-linecommentsforquickexplanationsandmulti-linecommentsfordetaileddescriptions.3)Bestpracticesinclud
Javascript Comments: short explanation
Jun 19, 2025 am 12:40 AM
JavaScriptcommentsareessentialformaintaining,reading,andguidingcodeexecution.1)Single-linecommentsareusedforquickexplanations.2)Multi-linecommentsexplaincomplexlogicorprovidedetaileddocumentation.3)Inlinecommentsclarifyspecificpartsofcode.Bestpractic
JavaScript Data Types: A Deep Dive
Jun 13, 2025 am 12:10 AM
JavaScripthasseveralprimitivedatatypes:Number,String,Boolean,Undefined,Null,Symbol,andBigInt,andnon-primitivetypeslikeObjectandArray.Understandingtheseiscrucialforwritingefficient,bug-freecode:1)Numberusesa64-bitformat,leadingtofloating-pointissuesli
JavaScript vs. Java: A Comprehensive Comparison for Developers
Jun 20, 2025 am 12:21 AM
JavaScriptispreferredforwebdevelopment,whileJavaisbetterforlarge-scalebackendsystemsandAndroidapps.1)JavaScriptexcelsincreatinginteractivewebexperienceswithitsdynamicnatureandDOMmanipulation.2)Javaoffersstrongtypingandobject-orientedfeatures,idealfor
How to work with dates and times in js?
Jul 01, 2025 am 01:27 AM
The following points should be noted when processing dates and time in JavaScript: 1. There are many ways to create Date objects. It is recommended to use ISO format strings to ensure compatibility; 2. Get and set time information can be obtained and set methods, and note that the month starts from 0; 3. Manually formatting dates requires strings, and third-party libraries can also be used; 4. It is recommended to use libraries that support time zones, such as Luxon. Mastering these key points can effectively avoid common mistakes.
JavaScript: Exploring Data Types for Efficient Coding
Jun 20, 2025 am 12:46 AM
JavaScripthassevenfundamentaldatatypes:number,string,boolean,undefined,null,object,andsymbol.1)Numbersuseadouble-precisionformat,usefulforwidevaluerangesbutbecautiouswithfloating-pointarithmetic.2)Stringsareimmutable,useefficientconcatenationmethodsf
