Author: John Au-Yeung

Sometimes, we want to click a button programmatically with JavaScript.

In this article, we’ll look at how to click a button programmatically with JavaScript.

How to click a button programmatically with JavaScript?

To click a button programmatically with JavaScript, we can call the click method.

For instance, we write

const userImage = document.getElementById("imageOtherUser");
const hangoutButton = document.getElementById("hangoutButtonId");
userImage.onclick = () => {
  hangoutButton.click();
};

to select the buttons with getElementById.

Then we add a click event handler to the userImage button by setting its onclick property to a function that calls hangoutButton.click.

This will click on the hangoutButton button programmatically.

Conclusion

To click a button programmatically with JavaScript, we can call the click method.

Sometimes, we want to access a variable of iframe from parent with JavaScript.

In this article, we’ll look at how to access a variable of iframe from parent with JavaScript.

How to access a variable of iframe from parent with JavaScript?

To access a variable of iframe from parent with JavaScript, we use the contentWindow property.

For instance, we write

const check = document.getElementById("iframeid").contentWindow.a;

to select the iframe with getElementById in the parent page’s code.

And then we get the iframe’s window object with contentWindow.

Then we get the x global variable from contentWindow.

Conclusion

To access a variable of iframe from parent with JavaScript, we use the contentWindow property.

Sometimes, we want to get contents of a text file from AWS S3 using a Lambda function with JavaScript.

In this article, we’ll look at how to get contents of a text file from AWS S3 using a Lambda function with JavaScript.

How to get contents of a text file from AWS S3 using a Lambda function with JavaScript?

To get contents of a text file from AWS S3 using a Lambda function with JavaScript, we use the getObject method.

For instance, we write

const AWS = require("aws-sdk");
const s3 = new AWS.S3();

const handler = async (event, context) => {
  const Bucket = event.Records[0].s3.bucket.name;
  const Key = decodeURIComponent(
    event.Records[0].s3.object.key.replace(/\+/g, " ")
  );
  const data = await s3.getObject({ Bucket, Key }).promise();
  console.log(data.Body.toString("ascii"));
};

to define the handler function.

In it, we get the Bucket1 and Key values from event.Records[0].

We replace the key’s slashes with spaces.

Then we call getObject to get the file by the Bucket and Key.

And then we get the file contents as a string with data.Body.toString.

Conclusion

To get contents of a text file from AWS S3 using a Lambda function with JavaScript, we use the getObject method.

Sometimes, we want to fix Jest failing with "Unexpected token *" on import statement with JavaScript.

In this article, we’ll look at how to fix Jest failing with "Unexpected token *" on import statement with JavaScript.

How to fix Jest failing with "Unexpected token *" on import statement with JavaScript?

To fix Jest failing with "Unexpected token *" on import statement with JavaScript, we transpile modules that cause the error.

For instance, we write

{
  "jest": {
    "preset": "react-native",
    "transformIgnorePatterns": [
      "node_modules/(?!(jest-)?react-native|react-(native|universal|navigation)-(.*)|@react-native-community/(.*)|@react-navigation/(.*)|bs-platform|(@[a-zA-Z]+/)?(bs|reason|rescript)-(.*)+)"
    ]
  }
}

to add the transformIgnorePatterns property into the jest.config.js file.

We use transformIgnorePatterns to ignore the path patterns of the modules that don’t need to be transpiled.

Conclusion

To fix Jest failing with "Unexpected token *" on import statement with JavaScript, we transpile modules that cause the error.

Sometimes, we want to check if writeFileSync successfully wrote the file with Node.js and JavaScript.

In this article, we’ll look at how to check if writeFileSync successfully wrote the file with Node.js and JavaScript.

How to check if writeFileSync successfully wrote the file with Node.js and JavaScript?

To check if writeFileSync successfully wrote the file with Node.js and JavaScript, we use the exists method.

For instance, we write

fs.exists(file, (exists) => {
  if (exists) {
    fs.writeFile(file, content, "utf-8", (err) => {
      if (err) {
        console.log("failed to save");
      } else {
        console.log("succeeded in saving");
      }
    });
  } else {
    console.log("file does not exist");
  }
});

to call fs.exists with the file path string to check if the file at the path exists.

The callback has the exists parameter which is true is the file exists at the path.

We call fs.writeFile when exists is true, which means the file exists.

Conclusion

To check if writeFileSync successfully wrote the file with Node.js and JavaScript, we use the exists method.