Categories

## How to Calculate a Person’s Age from Someone’s Birthday with JavaScript?

Sometimes, we want to calculate a person’s age from someone’s birthday with JavaScript.

In this article, we’ll look at how to calculate a person’s age from someone’s birthday with JavaScript.

### Calculate a Person’s Age from Someone’s Birthday with JavaScript

To calculate a person’s age from someone’s birthday with JavaScript, we can use native JavaScript date methods.

For instance, we can write:

``````const getAge = (d1, d2 = new Date()) => {
const diff = d2.getTime() - d1.getTime();
return Math.floor(diff / (1000 * 60 * 60 * 24 * 365.25));
}

console.log(getAge(new Date(1988, 10, 3)));
``````

We create the `getAge` function that takes 2 dates `d1` and `d2` .

Then we subtract the timestamps of them that we got with `getTime` with:

``````const diff = d2.getTime() - d1.getTime();
``````

And then we divide `diff` with `1000 * 60 * 60 * 24 * 365.25` to convert `diff` to the number of years differences, which is the person’s age.

Therefore, the console log should log 32.

### Conclusion

To calculate a person’s age from someone’s birthday with JavaScript, we can use native JavaScript date methods.

Categories

## How to Get the Current Time in Nanoseconds Using JavaScript?

Sometimes, we want to get the current time in nanoseconds using JavaScript.

In this article, we’ll look at how to get the current time in nanoseconds using JavaScript.

### Get the Current Time in Nanoseconds Using JavaScript

To get the current time in nanoseconds using JavaScript, we can use the `window.performance.now` method and `window.performance.timing.navigationStart` properties.

For instance, we can write:

``````const ms = window.performance.timing.navigationStart + window.performance.now()
const ns = ms / 0.001
console.log(ns)
``````

to get the current timestamp in nanoseconds.

`window.performance.timing.navigationStart` returns the timestamp in milliseconds when we run the code.

And `window.performance.now` returns the number of nanoseconds since the code has run.

Then to convert the timestamp in milliseconds to nanoseconds, we divide `ms` by 0.001.

### Conclusion

To get the current time in nanoseconds using JavaScript, we can use the `window.performance.now` method and `window.performance.timing.navigationStart` properties.

Categories

## How to Set a Button’s Value Using JavaScript?

Sometimes, we want to set a button’s value using JavaScript.

In this article, we’ll look at how to set a button’s value using JavaScript.

### Set a Button’s Value Using JavaScript

To set a button’s value using JavaScript, we can set the `innerHTML` property of the button.

For instance, if we have the following HTML:

``````<form>
<button name="submit-button">Original<br>Text</button>
</form>
``````

We can write:

``````const form = document.querySelector('form')
form.elements["submit-button"].innerHTML = 'submit'
``````

to get the form with `document.querySelector` .

Then we get the button with the `name` attribute set to `submit-button` with:

``````form.elements["submit-button"]
``````

And we set the `innerHTML` property of it to `'submit'` .

Therefore, the button in the form would have ‘submit’ as its text content.

### Conclusion

To set a button’s value using JavaScript, we can set the `innerHTML` property of the button.

Categories

## How to Count the Number of Occurrences for Each Character in a JavaScript String?

Sometimes, we want to count the number of occurrences for each character in a JavaScript string.

In this article, we’ll look at how to count the number of occurrences for each character in a JavaScript string.

### Count the Number of Occurrences for Each Character in a JavaScript String

To count the number of occurrences for each char in a JavaScript string, we can create an object that keeps track of how many characters are in each string.

Then we can loop through each character of the string with a for-of loop.

For instance, we can write:

``````const countChar = (str) => {
const counts = {};
for (const s of str) {
if (counts[s]) {
counts[s]++
} else {
counts[s] = 1
}
}
return counts;
}

const str = "I want to count the number of occurences of each char in this string";
console.log(countChar(str))
``````

to count the number of occurrences in each character in `str` with the `countChar` function.

Then function loops through each character of string `str` with the for-of loop.

Next, we create the `counts` object to keep track of the count of each character.

Then if `count[s]` exists, we increment it by 1.

Otherwise, we set `count[s]` to 1.

And then when the loop is done, we return the `counts` object.

### Conclusion

To count the number of occurrences for each char in a JavaScript string, we can create an object that keeps track of how many characters are in each string.

Then we can loop through each character of the string with a for-of loop.

Categories

## How to Get the Text Node After an HTML Element with JavaScript?

Sometimes, we want to get the text node after an HTML element with JavaScript.

In this article, we’ll look at how to get the text node after an HTML element with JavaScript.

### Get the Text Node After an HTML Element with JavaScript

To get the text node after an HTML element with JavaScript, we can use the `nextsubling.nodeValue` property to get the text content of the text node after a given element.

For instance, if we have the following HTML:

``````<input type="checkbox" name='something' value='v1' /> All the world <br />
``````

Then we can get the node value of the element after it by writing:

``````const text = document.querySelector('input[name="something"]').nextSibling.nodeValue
console.log(text)
``````

We select the input with:

``````document.querySelector('input[name="something"]')
``````

Then we use the `nextSibling.nodeValue` property of it to get the text node value next to it, which is `'All the world'` .

### Conclusion

To get the text node after an HTML element with JavaScript, we can use the `nextsubling.nodeValue` property to get the text content of the text node after a given element.