Category: JavaScript

Sometimes, we want to get the number of elements in a JavaScript object.

In this article, we’ll look at how to get the number of elements in a JavaScript object.

How to get the number of elements in a JavaScript object?

To get the number of elements in a JavaScript object, we can use the Object.keys method.

For instance, we write

const count = Object.keys(obj).length;

to call Object.keys with obj to get an array with the key strings in obj.

Then we use the length property to get the number of properties in obj.

Conclusion

To get the number of elements in a JavaScript object, we can use the Object.keys method.

Sometimes, we want to get a pixel from HTML Canvas with JavaScript.

In this article, we’ll look at how to get a pixel from HTML Canvas with JavaScript.

How to get a pixel from HTML Canvas with JavaScript?

To get a pixel from HTML Canvas with JavaScript, we use the canvas context getImageData method.

For instance, we write

const [r, g, b] = context.getImageData(x, y, 1, 1).data;

to call the canvas context.getImageData method with the x and y coordinates of the pixel we want to get.

Then we get the r, g and b values of the pixel from the data array property.

Conclusion

To get a pixel from HTML Canvas with JavaScript, we use the canvas context getImageData method.

Sometimes, we want to make a number a percentage with JavaScript.

In this article, we’ll look at how to make a number a percentage with JavaScript.

How to make a number a percentage with JavaScript?

To make a number a percentage with JavaScript, we can get the quotient of 2 numbers and multiply that by 100.

For instance, we write

const number1 = 4.98;
const number2 = 5.98;

console.log(Math.floor((number1 / number2) * 100));

to divide number1 by number2 and multiply the quotient by 100.

Then we call Math.floor on the product to get the floor of it.

Conclusion

To make a number a percentage with JavaScript, we can get the quotient of 2 numbers and multiply that by 100.

Sometimes, we want to get 30 days prior to current date with JavaScript.

In this article, we’ll look at how to get 30 days prior to current date with JavaScript.

How to get 30 days prior to current date with JavaScript?

To get 30 days prior to current date with JavaScript, we can use the setDate and getDate methods.

For instance, we write

const today = new Date();
const priorDate = new Date(new Date().setDate(today.getDate() - 30));

console.log(today);
console.log(priorDate);

to get the day of the month of today‘s date with getDate.

Then we subtract 30 from it and use the difference as the argument for setDate.

Then we copy the new date value by passing the returned Date object to the Date constructor.

Conclusion

To get 30 days prior to current date with JavaScript, we can use the setDate and getDate methods.