Category: JavaScript Answers

Sometimes, we want to compare arrays of objects in JavaScript.

In this article, we’ll look at how to compare arrays of objects in JavaScript.

How to compare arrays of objects in JavaScript?

To compare arrays of objects in JavaScript, we can use some array properties and methods.

For instance, we write

const obj1 = { name: "John", age: 33 };
const obj2 = { age: 33, name: "John" };
const obj3 = { name: "John", age: 45 };

const arr1 = [obj1, obj1];
const arr2 = [obj1, obj2];
const arr3 = [obj1, obj3];

const objectsEqual = (o1, o2) =>
  typeof o1 === "object" && Object.keys(o1).length > 0
    ? Object.keys(o1).length === Object.keys(o2).length &&
      Object.keys(o1).every((p) => objectsEqual(o1[p], o2[p]))
    : o1 === o2;

const arraysEqual = (a1, a2) =>
  a1.length === a2.length && a1.every((o, idx) => objectsEqual(o, a2[idx]));

console.log(arraysEqual(arr1, arr2)); // true
console.log(arraysEqual(arr1, arr3));

to define the objectsEqual function that recursive checks if every property in objects o1 and o2 are equal.

We do this by checking if o1 is an object.

If it is, then we check if the number of properties of o1 and o2 are the same with

Object.keys(o1).length === Object.keys(o2).length

And then we use

Object.keys(o1).every((p) => objectsEqual(o1[p], o2[p]))

to check if each property is equal.

We call objectsEqual with the property p of o1 and o2 since they’re objects.

Otherwise, we compare the values directly with

o1 === o2

Then we define the arrayEqual function that checks if array a1 and a2‘s length and content are equal with

a1.length === a2.length && a1.every((o, idx) => objectsEqual(o, a2[idx]);

Conclusion

To compare arrays of objects in JavaScript, we can use some array properties and methods.

Sometimes, we want to replace a regex capture group with uppercase in JavaScript.

In this article, we’ll look at how to replace a regex capture group with uppercase in JavaScript.

How to replace a regex capture group with uppercase in JavaScript?

To replace a regex capture group with uppercase in JavaScript, we call string replace with a callback.

For instance, we write

const r = a.replace(/(f)/, (v) => {
  return v.toUpperCase();
});

to call a string’s replace to find the capturing group with f inside.

And we replace the matches values with the value converted to upper case with toUpperCase.

Conclusion

To replace a regex capture group with uppercase in JavaScript, we call string replace with a callback.

Sometimes, we want to create JSON with JavaScript for loop.

In this article, we’ll look at how to create JSON with JavaScript for loop.

How to create JSON with JavaScript for loop?

To create JSON with JavaScript for loop, we can use a for-of loop.

For instance, we write

const sels = [
  //...
];
const json = {};

for (const sel of sels) {
  json[sel.id] = sel.value;
}

to loop through the object entries in the sels array with a for-of loop.

In it, we get the entry being looped through with sel.

We add the sel.id property into json and then assign sel.value to it.

sel.id returned string value would be the property name.

Conclusion

To create JSON with JavaScript for loop, we can use a for-of loop.

Sometimes, we want to turn off antialiasing on an HTML canvas element with JavaScript.

In this article, we’ll look at how to turn off antialiasing on an HTML canvas element with JavaScript.

How to turn off antialiasing on an HTML canvas element with JavaScript?

To turn off antialiasing on an HTML canvas element with JavaScript, we can set context.imageSmoothingEnabled to false to turn off antialiasing for images.

For instance, we write

context.imageSmoothingEnabled = false;

to set the canvas’ context‘s imageSmoothingEnabled property to false to disable antialiasing on images in the canvas.

Conclusion

To turn off antialiasing on an HTML canvas element with JavaScript, we can set context.imageSmoothingEnabled to false to turn off antialiasing for images.

Sometimes,. we want to round to a number of decimal places, but strip extra zeros with JavaScript.

In this article, we’ll look at how to round to a number of decimal places, but strip extra zeros with JavaScript.

How to round to a number of decimal places, but strip extra zeros with JavaScript?

To round to a number of decimal places, but strip extra zeros with JavaScript, we use the number toFixed method and the parseFloat function.

For instance, we write

const n = parseFloat((1.005).toFixed(15));

to call (1.005).toFixed(15) to round 1.005 to 15 decimal places.

Then we pass the returned number string into parseFloat to return the rounded number without the extra trailing zeroes.

Conclusion

To round to a number of decimal places, but strip extra zeros with JavaScript, we use the number toFixed method and the parseFloat function.