Category: JavaScript

Sometimes, we want to get pixel color from an image with JavaScript.

In this article, we’ll look at how to get pixel color from an image with JavaScript.

How to get pixel color from an image with JavaScript?

To get pixel color from an image with JavaScript, we can put the image in the canvas.

For instance, we write:

const myImg = new Image();
myImg.crossOrigin = "Anonymous";
myImg.onload = () => {
  const context = document.createElement('canvas').getContext('2d');
  context.drawImage(myImg, 0, 0);
  const {
    data
  } = context.getImageData(10, 10, 1, 1);
  console.log(data)
}
myImg.src = 'https://picsum.photos/200/300';

In myImg.onload we get the pixel data from the canvas by creating a canvas element with createElement.

Then we get the context with getContext.

Next, we call drawImage to draw the image.

And then we call getImageData with the x, y coordinates of the pixel to get as the first 2 arguments.

As a result, we see that data is a Uint8ClampedArray.

Conclusion

To get pixel color from an image with JavaScript, we can put the image in the canvas.

Sometimes, we want to convert a JavaScript date to SQL date object.

In this article, we’ll look at how to convert a JavaScript date to SQL date object.

How to convert a JavaScript date to SQL date object?

To convert a JavaScript date to SQL date object, we can use the JavaScript date’s toLocaleString method.

For instance, we write:

const date = (new Date(2022, 1, 1)).toLocaleString("en-US")
console.log(date)

to call toLocaleString with 'en-US' to convert return a date string formatted for the US English locale.

Therefore, date is '2/1/2022, 12:00:00 AM'.

Conclusion

To convert a JavaScript date to SQL date object, we can use the JavaScript date’s toLocaleString method.

Sometimes, we want to efficiently compare two integer arrays and find the items in both arrays with JavaScript.

In this article, we’ll look at how to efficiently compare two integer arrays and find the items in both arrays with JavaScript.

How to efficiently compare two integer arrays and find the items in both arrays with JavaScript?

To efficiently compare two integer arrays and find the items in both arrays with JavaScript, we can use some JavaScript array methods.

For instance, we write:

const a1 = [15, 551, 25, 910, 11]
const a2 = [25, 11, 785, 880, 15]
const inBoth = a1.filter(a => a2.includes(a))
console.log(inBoth)

to call a1.filter with a callback that checks if a1 array entry a is in a2 with a2.includes.

Therefore, inBoth is [15, 25, 11].

Conclusion

To efficiently compare two integer arrays and find the items in both arrays with JavaScript, we can use some JavaScript array methods.

Sometimes, we want to extract the user name from an email address using JavaScript.

In this article, we’ll look at how to extract the user name from an email address using JavaScript.

How to extract the user name from an email address using JavaScript?

To extract the user name from an email address using JavaScript, we can use a regex to get the part before the @ with the string match method.

For instance, we write:

const str = "someone@example.com";
const nameMatch = str.match(/^([^@]*)@/);
console.log(nameMatch)

to call str.match with /^([^@]*)@/ to get the part of the email address before the @.

Therefore, nameMatch is ['someone@', 'someone', index: 0, input: 'someone@example.com', groups: undefined].

Conclusion

To extract the user name from an email address using JavaScript, we can use a regex to get the part before the @ with the string match method.

Sometimes, we want to retrieve the last day of the year in JavaScript.

In this article, we’ll look at how to retrieve the last day of the year in JavaScript.

How to retrieve the last day of the year in JavaScript?

To retrieve the last day of the year in JavaScript, we can use the date methods.

For instance, we write:

const lastDayOfYear = new Date(new Date().getFullYear(), 11, 31)
console.log(lastDayOfYear)

to create a Date instance with the 4 digit year number of the current year that we get from getFullYear.

The 2nd argument is 11 for December and the last argument is 31 for the 31st day of the month.

Therefore, lastDayOfYear is Sat Dec 31 2022 00:00:00 GMT-0800 (Pacific Standard Time) if today’s year is 2022.

Conclusion

To retrieve the last day of the year in JavaScript, we can use the date methods.