Category: JavaScript Answers

Sometimes, we want to access event to call preventdefault from custom function originating from onclick with JavaScript.

In this article, we’ll look at how to access event to call preventdefault from custom function originating from onclick with JavaScript.

How to access event to call preventdefault from custom function originating from onclick with JavaScript?

To access event to call preventdefault from custom function originating from onclick with JavaScript, we get the event object from the event handler function’s parameter.

For instance, we write

<a href="#">Click to say Hi</a>

to add a link.

Then we show an alert when we click on the link by writing

const a = document.querySelector("a");
a.onclick = (e) => {
  e.preventDefault();
  alert("hi");
};

We select the link with querySelector.

Then we set its onclick property to a function that calls e.preventDefault to stop the default behavior of navigation to the URL set as the href attribute’s value.

Instead, we call alert with 'hi' to show an alert box.

Conclusion

To access event to call preventdefault from custom function originating from onclick with JavaScript, we get the event object from the event handler function’s parameter.

Sometimes, we want to open a given URL in a new tab by clicking a button with JavaScript.

In this article, we’ll look at how to open a given URL in a new tab by clicking a button with JavaScript.

How to open a given URL in a new tab by clicking a button with JavaScript?

To open a given URL in a new tab by clicking a button with JavaScript, we call window.open with the '_blank' argument.

For instance, we write

window.open(url, "_blank");

to call window.open to open the url in a new tab with '_blank'.

Conclusion

To open a given URL in a new tab by clicking a button with JavaScript, we call window.open with the '_blank' argument.

Sometimes, we want to get average color of image via JavaScript.

In this article, we’ll look at how to get average color of image via JavaScript.

How to get average color of image via JavaScript?

To get average color of image via JavaScript, we can put the image in a canvas and then use the canvas context getImageData method.

For instance, we write

const getAverageRgb = (img) => {
  const context = document.createElement("canvas").getContext("2d");
  if (typeof img === "string") {
    const img = new Image();
    img.setAttribute("crossOrigin", "");
    img.src = src;
    img.onload = () => {
      context.imageSmoothingEnabled = true;
      context.drawImage(img, 0, 0, 1, 1);
      console.log(context.getImageData(1, 1, 1, 1).data.slice(0, 3));
    };
  }
};

to define the getAverageRgb function.

In it, we create a canvas element with createElement and get its context with getContext.

Then we create the img image and set its onload property to a function that gets the average rgb value with getImageData.

Conclusion

To get average color of image via JavaScript, we can put the image in a canvas and then use the canvas context getImageData method.

Sometimes, we want to remove legend on charts with Chart.js v2 and JavaScript.

In this article, we’ll look at how to remove legend on charts with Chart.js v2 and JavaScript.

How to remove legend on charts with Chart.js v2 and JavaScript?

To remove legend on charts with Chart.js v2 and JavaScript, we can set the options.legend to false.

For instance, we write

const chart1 = new Chart(canvas, {
  type: "pie",
  data: data,
  options: {
    legend: {
      display: false,
    },
    tooltips: {
      enabled: false,
    },
  },
});

to create the Chart object with the options.legend property set to false to disable the legend.

Conclusion

To remove legend on charts with Chart.js v2 and JavaScript, we can set the options.legend to false.

Sometimes, we want to fix Firebase permission denied with JavaScript.

In this article, we’ll look at how to fix Firebase permission denied with JavaScript.

How to fix Firebase permission denied with JavaScript?

To fix Firebase permission denied with JavaScript, we can sign in before we do any database operations.

For instance, we write

firebase
  .auth()
  .signInAnonymously()
  .catch((error) => {
    const errorCode = error.code;
    const errorMessage = error.message;
    // ...
  });

to call signInAnonymously to sign in as a anonymous user.

Then we call catch with a callback to catch any errors.

Conclusion

To fix Firebase permission denied with JavaScript, we can sign in before we do any database operations.