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Vue provides a more general way to observe and respond to data changes on Vue instances: listening properties. 1. General usage <template> <div> <input v-model="question"> <span>{{ copyQuestion }}</span> </div> </template> <script> export default { data() { r ...

catalogue 1, Data types in JS 2, Methods of judging data types in JS 1. Using typeof 2. Using instanceof 3. Use object prototype. toString. call 4. Using constructor 1, Data types in JS ECMAScript has five simple data types (also known as basic data types): Undefined, Null, Boolean, Number, and String. There is also the complex data ...

In this article, you will see: Conceptual relationship among MySQL, SQL, ORM and serializeUse of sequenizeThe concept, usage, principle and difference of join table relation in sequenizeHow to optimize database query 1 Concept MySQL Most people know about MySQL and SQL. After all, it is written in textbooks. MySQL is a typical relational dat ...

follow [front end Xiaoao] , read more original technical articles Agent basis ES6 proxy and reflection provide developers with the ability to intercept and embed additional behavior into basic operationsA proxy is an abstraction of a target object. It can be used as a substitute for the target object, but it is completely independent of the ...

catalogue css Chapter 1 1 cascading style sheets 2 element 1. Replacement elements 2. Non replacement elements 3. Display mode of elements 3. Introduce css  1 link  2 @import  3 style 4 inline style 3 content in style sheet 1. Mark, note 2. Rules 3. Manufacturer prefix: 4. Processing blank: 4 media query 1. Grammar 2. Type of ...

Learning contents: forEach, slice and slice, and the remaining methods of array Study notes forEach Generally, we use the for loop to traverse the array JS also provides us with a method to traverse the array forEach() only supports browsers above IE8 The forEach() method requires a function as a parameter; This function is created by us, bu ...

background   When it comes to building tools, I often add the word "automation" before it, because building tools are used to make us stop doing mechanical things and liberate our hands. What is front-end automation? The code that front-end engineers need to maintain is extremely huge and complex, and the processes of code maintena ...

1, Prototype chain inheritance The key of prototype chain inheritance is to assign new Parent() to child Prototype, which means that when accessing the properties of the child object, if it cannot be found on the child, it will go to the child Prototype. If you can't find it, you'll go to parent Find it in prototype, so as to realize inheritan ...

146. What is the output? function getFruit(fruits) { console.log(fruits?.[1]?.[1]) } getFruit([['🍊', '🍌'], ['🍍']]) getFruit() getFruit([['🍍'], ['🍊', '🍌']]) Answer: D. this question mainly focuses on the optional chain operator. As long as it does not exist, it returns undefined, so choose D. 147. What is the output? class Ca ...

Inheritance of styles (p38) 1. Style inheritance: the style we set for an element will also be applied to the descendant elements. 2. Inheritance occurs between descendant elements and descendants. 3. The design of inheritance is to facilitate our development. Using inheritance, we can uniformly set some general styles to the common ance ...