Category: JavaScript Answers

Sometimes, we want to get text area input value with JavaScript.

In this article, we’ll look at how to get text area input value with JavaScript.

How to get text area input value with JavaScript?

To get text area input value with JavaScript, we use the value property.

For instance, we write

<textarea id="textArea"></textarea>

to add the textarea element.

Then we write

document.getElementById("textArea").value = "text";

to select the text area with getElementById.

And then we set its value property to set its input value.

We use the same property to get its input value.

Conclusion

To get text area input value with JavaScript, we use the value property.

Sometimes, we want to download a file from Amazon S3 bucket with JavaScript.

In this article, we’ll look at how to download a file from Amazon S3 bucket with JavaScript.

How to download a file from Amazon S3 bucket with JavaScript?

To download a file from Amazon S3 bucket with JavaScript, we use the AWS Node.js API.

For instance, we write

const AWS = require("aws-sdk");

AWS.config.update({
  accessKeyId: "your key",
  secretAccessKey: "your secret key",
});

const s3 = new AWS.S3();

s3.getObject({ Bucket: "my-bucket", Key: "my-picture.jpg" }, (error, data) => {
  if (error !== null) {
    console.log("Failed to retrieve an object: ", error);
  } else {
    console.log("Loaded " + data.ContentLength + " bytes");
  }
});

to call AWS.config.update to set the keys for accessing S3.

to call getObject with with the bucket and key name to download the file with the given key in the given buckey.

We get the error if there is any.

Conclusion

To download a file from Amazon S3 bucket with JavaScript, we use the AWS Node.js API.

Sometimes, we want to submit two forms with one button with JavaScript.

In this article, we’ll look at how to submit two forms with one button with JavaScript.

How to submit two forms with one button with JavaScript?

To submit two forms with one button with JavaScript, we call submit on each form on click.

For instance, we write

<input type="button" value="Click Me" onclick="submitForms()" />

to add a button.

We set onclick to submitForms() to call submitForms on click.

Then we write

function submitForms() {
  document.getElementById("form1").submit();
  document.getElementById("form2").submit();
}

to get each form with getElementById and call submit on each form.

Conclusion

To submit two forms with one button with JavaScript, we call submit on each form on click.

Sometimes, we want to merge JavaScript objects in array with same key.

In this article, we’ll look at how to merge JavaScript objects in array with same key.

How to merge JavaScript objects in array with same key?

To merge JavaScript objects in array with same key, we use some array methods.

For instance, we write

const array = [
  { name: "foo1", value: "val1" },
  { name: "foo1", value: ["val2", "val3"] },
  { name: "foo2", value: "val4" },
];

const result = array.reduce((acc, { name, value }) => {
  acc[name] ??= { name, value: [] };
  if (Array.isArray(value)) {
    acc[name].value = acc[name].value.concat(value);
  } else {
    acc[name].value.push(value);
  }
  return acc;
}, {});

console.log(Object.values(result));

to call array.reduce with a callback that gets the values from objects in array and put them in as the property of the acc object.

In it, we assign { name, value: [] } to acc[name] if acc[name] is undefined.

Then if value is an array, we call concat to put value in the acc[name].value array.

Otherwise, we call push to add value into acc[name].value.

acc is returned at the end.

Conclusion

To merge JavaScript objects in array with same key, we use some array methods.

Sometimes, we want to reconnect to WebSocket after close connection with JavaScript.

In this article, we’ll look at how to reconnect to WebSocket after close connection with JavaScript.

How to reconnect to WebSocket after close connection with JavaScript?

To reconnect to WebSocket after close connection with JavaScript, we create a new WebSocket object when the connection is closed.

For instance, we write

const startWebsocket = () => {
  let ws = new WebSocket("ws://localhost:8080");

  ws.onmessage = (e) => {
    console.log("websocket message event:", e);
  };

  ws.onclose = () => {
    ws = null;
    setTimeout(startWebsocket, 5000);
  };
};

startWebsocket();

to define the startWebsocket function.

In it, we create a new WebSocket object to start the connection.

Then we set its onclose property to a function that calls startWebsocket to restart the connection.

Conclusion

To reconnect to WebSocket after close connection with JavaScript, we create a new WebSocket object when the connection is closed.