Category: JavaScript Answers

Sometimes, we want to use the window.open method to open a mailto URL with JavaScript.

In this article, we’ll look at how to use the window.open method to open a mailto URL with JavaScript.

Use the window.open Method to Open a mailto URL with JavaScript

To use the window.open method to open a mailto URL, we can call window.open with '_self' as the 2nd argument.

For instance, we write:

const emailTo = 'example@example.com'
const emailCC = 'cc@example.com'
const emailSub = 'subject'
const emailBody = 'body'
window.open(`mailto:${emailTo}?cc=${emailCC}&subject=${emailSub}&body=${emailBody}`, '_self');

We set the emailTo, emailCC, emailSub and emailBody variables to the values we want.

emailTo is the email address to mail to.

emailCC is the email address to CC.

emailSub is the subject of the email.

emailBody is the email body.

We call window.open with ‘mailto:${emailTo}?cc=${emailCC}&subject=${emailSub}&body=${emailBody}‘ as the first argument to open that URL.

The 2nd argument is '_self' so it won’t open a new tab.

Now when we run the code, we should see the default email client open up with the receiver’s address, CC address, subject and body filled in.

Conclusion

To use the window.open method to open a mailto URL, we can call window.open with '_self' as the 2nd argument.

Sometimes, we want to change font size with JavaScript.

In this article, we’ll look at how to change font size with JavaScript.

Change Font Size with JavaScript

To change font size with JavaScript, we can set the style.fontSize property of the element.

For instance, if we have the following HTML:

<span>hello</span>

Then we write the following JavaScript code:

const span = document.querySelector("span");
span.style.fontSize = "25px";

to select the span element and set the font size of its content.

We select the element with document.querySelector and assign the returned element to span.

Then we set span.style.fontSize to '25px' to set the font size of its content to 25px.

Now we should see larger text displayed.

Conclusion

To change font size with JavaScript, we can set the style.fontSize property of the element.

Sometimes, we want to change image opacity using JavaScript.

In this article, we’ll look at how to change image opacity using JavaScript.

Change Image Opacity Using JavaScript

To change image opacity using JavaScript, we can use the setAttribute method.

For instance, if we have the following image:

<img src='https://picsum.photos/200'>

We write:

document
  .querySelector("img")
  .setAttribute("style", "opacity:0.5; -moz-opacity:0.5; filter:alpha(opacity=50)");

to select the img element with document.querySelector("img").

Then we call setAttribute with 'style' and "opacity:0.5; -moz-opacity:0.5; filter:alpha(opacity=50)" to set the style attribute of the img element to opacity:0.5; -moz-opacity:0.5; filter:alpha(opacity=50).

Therefore, we see that the resulting image displayed is translucent.

Conclusion

To change image opacity using JavaScript, we can use the setAttribute method.

Sometimes, we want to round time to the nearest quarter-hour in JavaScript

In this article, we’ll look at how to round time to the nearest quarter-hour in JavaScript.

Round Time to the Nearest Quarter-Hour in JavaScript

To round time to the nearest quarter-hour in JavaScript, we can use existing JavaScript date methods.

For instance, we can write:

const roundTimeQuarterHour = (time) => {
  const timeToReturn = new Date(time);
  timeToReturn.setMilliseconds(Math.round(timeToReturn.getMilliseconds() / 1000) * 1000);
  timeToReturn.setSeconds(Math.round(timeToReturn.getSeconds() / 60) * 60);
  timeToReturn.setMinutes(Math.round(timeToReturn.getMinutes() / 15) * 15);
  return timeToReturn;
}
const dt = new Date(2021, 1, 1, 1, 13, 1, 1)
console.log(roundTimeQuarterHour(dt))

to create the roundTimeQuarterHour function that takes the time to round.

In the function, we convert that to a date object with the Date constructor top create the timeToReturn date object.

Then we call setMilliseconds to set timeToReturn the nearest 1000 milliseconds.

Next, we call setSeconds to round timeToReturn to the nearest 60 seconds.

Then, we call setNMinutes to round timeToReturn to the nearest 15 minutes by getting the number of minutes from the time with getMinutes , dividing that by 15 and multiplying that by 15 again.

Therefore, the console log should log:

Mon Feb 01 2021 01:15:00 GMT-0800 (Pacific Standard Time)

Conclusion

To round time to the nearest quarter-hour in JavaScript, we can use existing JavaScript date methods.