這將回傳未定義：（節點：3196）UnhandledPromiseRejectionWarning：TypeError：無法讀取未定義的屬性“myArray”

這是我的代碼：

https://github.com/DavidNyan10/NewProject

const fs = require('fs');
const csv = require('csv-parser')

const myString = new Promise((resolve, reject) => {
    resolve('John');
});

class myClass{
    constructor(filename){
        this.myArray = [];
        this.myArray.push(new Promise((res) => {
            fs.createReadStream('filename')
                  .pipe(csv(['FirstName', 'LastName', 'Address', 'Town', 'Country', 'Postcode']))
                  .on('data', (data) => {
                    return(data);
                  })
          }))
    }
    async myFunction() {
        for(let i = 0; i < this.myArray.length; i  ) {
            if (myString.includes(this.myArray[i]['phrase'])){
                if (this.cooled_down(i)){
                    this.approve(i, myString);
                }
            }
        }
    }
    
    cooled_down(i){
        dictionary = this.myArray[i]
        if (!dictionary.keys().includes('approved')){
            // Means we have never approved on this person!
            return True;
        } else{
            now = datetime.now();
            duration = now - datetime.fromtimestamp(dictionary['approved']);
            duration_seconds = duration.total_seconds();
            hours = divmod(duration_seconds, 3600)[0];
            if (hours >= 24){
                return True;
            } else{
                console.log("Couldn't approve "   dictionary['FirstName']   "Cool Down time: "   24 - hours);
            }
        }
        return False;
    }

    approve(i, myString){
        dictionary = this.myArray[i];
        try{
            setTimeout(function(){
                console.log(myString);
                console.log(dictionary['FirstName'])
                console.log(dictionary['Postcode'])
            }, 60 * 60 * 3);
        }catch(e){
            console.log(e);
        }

        now = datetime.now();
        this.myArray[i]['approved'] = now.timestamp();
    }
}

myObj = new myClass("myCSV.csv");
myString.then(myObj.myFunction);

它一直在說

(node:3196) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'myArray' of undefined
    at myFunction (D:\projects\newproject\index.js:20:30)
    at processTicksAndRejections (internal/process/task_queues.js:95:5)
(Use `node --trace-warnings ...` to show where the warning was created)
(node:3196) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 2)
(node:3196) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

但是正如您可以清楚地看到的那樣，this.myArray在第 10 行中明確定義了。

到底是怎么回事？

我對 javascript 類和物件很陌生，所以如果我看起來很笨，我很抱歉。

另外，有什么想法可以使第 11-17 行更好嗎？我只是將 csv 放入一個陣列中，但我不知道這是否是最好的方法。

uj5u.com熱心網友回復：

你打電話給myString.then(myObj.myFunction)。這是將this關鍵字從更改myObj為其他內容。如果要保留this關鍵字的背景關系，則需要this手動系結或呼叫該函式而不是將其傳遞給then回呼。例子：

// Binding `this` to object:
myString.then(myObj.myFunction.bind(myObj));

// or
// Calling the function inside anonymous function instead 
// of passing it to `then` callback:
myString.then(() => myObj.myFunction());

標籤：javascript 节点.js 类型错误

上一篇：用陣列過濾貓鼬陣列？

下一篇：在函式記憶體根特定的API請求