为什么我的javascript类实例中的方法看不到属性

Question

A property set in the constructor of a class is not available to other functions in that instance of the class

The class constructor takes an object as data as its argument. This is then saved as a property of the instance - all good.

const form = new Form({
  "name": "John",
  "description": "a good bloke",
  "box_id": 1
});

I can see that form.orginalData is the object passed however when I run

form.toString()

I get an empty object (set in the function called data)

Here is the example in full

 class Form { constructor(data) { this.orginalData = data for (let field in this.orginalData) { this[field] = data[field]; } } data() { let d = {}; for (let p in this.originalData) { d[p] = this[p]; } return d; } toString() { return JSON.stringify(this.data()); } } const form = new Form({ "name": "John", "description": "a good bloke", "box_id": 1 }); let message = document.getElementById('message'); form.name = 'Ian'; form.description = 'is a wicked man'; message.innerHTML = form.name + '<br/>'; message.innerHTML += form.description + '<br/>'; message.innerHTML += "orginalData:" + JSON.stringify(form.orginalData) + '<br/>' message.innerHTML += "<p>BUT if I run form.data() I get </p>" message.innerHTML += form.toString(); 

 #message { border: 1px solid blue; padding: 10px; } body { font-family: Sans-Serif; } 

 <h1> Class property persistance </h1> <p> output: </p> <div id="message"> Something went wrong </div> 

I am obviously missing something fairly fundamental

Answer 1

您得到空结果，因为originalData与orginalData