Category: JavaScript

Sometimes, we want to read in a local csv file in JavaScript.

In this article, we’ll look at how to read a csv file in JavaScript.

How read a csv file in JavaScript?

To read a csv file in JavaScript, we can use the FileReader constructor.

For instance, we write:

<input type="file">

to add a file input.

Then we write:

const input = document.querySelector('input')
const fileReader = new FileReader()
fileReader.onload = (e) => {
  console.log(e.target.result)
}

input.onchange = (e) => {
  const [file] = e.target.files
  fileReader.readAsBinaryString(file)
}

to select the input with querySelector.

Next, we create a FileReader instance.

Then we set its onload property to a function that logs the file content.

Next, we set input.onchange to a function that gets the selected file from e.target.files.

And then we call fileReader.readAsBinaryString to read the file.

Conclusion

To read in local csv file in JavaScript, we can use the FileReader constructor.

Sometimes, we want to loop over the child divs of a div and get the ids of the child divs with JavaScript.

In this article, we’ll look at how to loop over the child divs of a div and get the ids of the child divs with JavaScript.

How to loop over the child divs of a div and get the ids of the child divs with JavaScript?

To loop over the child divs of a div and get the ids of the child divs with JavaScript, we can use some DOM methods and the spread operator.

For instance, we write:

<div id="test">
  <div id="test-1"></div>
  <div id="test-2"></div>
  <div id="test-3"></div>
  <div id="test-4"></div>
</div>

to add a div with divs.

Then we write:

const childDivs = document.getElementById('test').getElementsByTagName('div');
const ids = [...childDivs].map(d => d.id)
console.log(ids)

to select all the child divs in the div with ID test with document.getElementById('test').getElementsByTagName('div').

Then we spread the returned node list into an array and call map with a callback to return the id attribute value from each div.

Therefore, ids is ["test-1", "test-2", "test-3", "test-4"].

Conclusion

To loop over the child divs of a div and get the ids of the child divs with JavaScript, we can use some DOM methods and the spread operator.

Sometimes, we want to assign a function to the property of a JavaScript object.

In this article, we’ll look at how to assign a function to the property of a JavaScript object.

How to assign a function to the property of a JavaScript object?

To assign a function to the property of a JavaScript object, we can use the assignment operator.

For instance, we write:

const obj = {}
obj.hello = () => {
  console.log('hello')
}
obj.hello()

to assign a function that logs 'hello' as the value of the obj.hello property.

Then we call the function with obj.hello().

Conclusion

To assign a function to the property of a JavaScript object, we can use the assignment operator.

Sometimes, we want to get a substring before a character with JavaScript.

In this article, we’ll look at how to get a substring before a character with JavaScript.

How to get a substring before a character with JavaScript?

To get a substring before a character with JavaScript, we can use the string’s split method.

For instance, we write:

const string = "foo-bar-baz"
const [foo] = string.split('-')
console.log(foo)

to call string.split with '-‘ to split the string by the dashes into a string array.

Then we get the word before the first dash with destructuring and assign it to foo.

Therefore, foo is 'foo'.

Conclusion

To get a substring before a character with JavaScript, we can use the string’s split method.

Sometimes, we want to add smooth auto scroll by with JavaScript.

In this article, we’ll look at how to add smooth auto scroll by with JavaScript.

How to add smooth auto scroll by with JavaScript?

To add smooth auto scroll by with JavaScript, we can call setTimeout recursively to scroll the page.

For instance, we write:

const pageScroll = () => {
  window.scrollBy(0, 1);
  setTimeout(pageScroll, 10);
}
pageScroll()

to define the pageScroll function to scroll the page.

In it, we call window.scrollBy to scroll 1 pixel down.

Then we call setTimeout with pageScroll and 10 to call pageScroll again 10 milliseconds later.

Conclusion

To add smooth auto scroll by with JavaScript, we can call setTimeout recursively to scroll the page.