Using js to implement the two-way binding function of data in Vue2.0

Object.defineProperty Understanding

grammar:

Object.defineProperty(obj, prop, descriptor)

obj The object for which the properties are to be defined.
prop The name of the property to define or modify
descriptor The property descriptor to be defined or modified

obj and prop are easy to understand. For example, we define a variable as

const o = {
    name:'xbhog'
}

Among them, obj refers to o, and prop refers to o.name. Next, let's take a look at the descriptor.

descriptor Some characteristics of the target object attributes (it is an object)
There are 6 parameters under descriptor
Parameter 1:
value: attribute value
Parameter 2:
writable: Whether the object property value can be modified. True allows. False does not allow.
Parameter 3:
configurable: Whether the object property can be deleted. True allows it. False does not allow it.
Parameter 4:
enumerable: Whether the object property can be enumerated
Parameter 5:
get(): is a function. When the property is accessed, the function is automatically called and the function return value is the value of the property.
Parameter 6:
set(): is a function that is automatically called when the property is modified. The function has one and only one parameter, the new value to be assigned

Note: The value attribute, writable attribute and get attribute, set attribute in the descriptor are mutually exclusive. Only one can exist.

Knowing the prerequisites, let's implement two-way binding of v-model in Vue

Let's look at the implementation code first:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Realize two-way data binding through js</title>
</head>
<body>
    
<input type="text"/><br>
<h1>Hello: <span>Update data</span></h1>


<!-- Realize two-way data binding through js -->
<script>
	// The method returns the first HTMLElement object in the document that matches the specified selector or selector group var ipt = document.querySelector('input');
    var p = document.querySelector('span');
	
	
    var data = {name:""};
	/* 
	    The oninput event is triggered when the user types something.
	    This event is triggered when the value of an <input> or <textarea> element changes.
	 */
    ipt.oninput = function(){
	// Pass the value in ipt.value to the value of data.name
        data.name = ipt.value;
    }
    //Hijack ipt.value
    Object.defineProperty(data,"name",{
    //Data subscription get(){
        return ipt.value; //The get method will be called when accessing},
    //Data hijacking //name:value
    set(value) {
        p.innerHTML = value;
        ipt.value = value;
    }   
})
</script>
</body>
</html>

First, we use document.querySelector to get the Html objects of the input and span tags, and then define a data object with the attribute name empty.

Use the oninput event listener to monitor user input (this event is triggered when the value of an <input> or <textarea> element changes).

Pass the value in ipt.value to the value of data.name;

data.name = ipt.value;

Use Object.defineProperty to hijack user input data.

get attribute: It is a function. When the attribute is accessed, the function is automatically called, and the function return value is the value of the attribute.
set property: is a function. When the property is modified, the function is automatically called. The function has one and only one parameter, the new value to be assigned.

Object.defineProperty(data,"name",{
    //Data subscription get(){
       return ipt.value; //When accessing data.name, the get method will be called to call ipt.value to get the current value},
    // Data hijacking set(value) { // The set method will be automatically called when setting data p.innerHTML = value;
        ipt.value = value;
    }

The effect is more obvious:

Set method:

Get method:

The final effect:

References:

https://blog.csdn.net/Doulvme/article/details/107978012
https://developer.mozilla.org/zh-CN/docs/Web/API/Document/querySelector
https://www.jianshu.com/p/6f589af16ad4
//www.jb51.net/article/217657.htm (recommended)

Summarize

This is the end of this article about using js to implement the two-way data binding function in Vue2.0. For more relevant content about using js to implement Vue2 two-way binding, please search for previous articles on 123WORDPRESS.COM or continue to browse the following related articles. I hope everyone will support 123WORDPRESS.COM in the future!

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