Getting the Input Value

Using Ramda to get and trim the input's text value, setting a default if nothing's passed. (5 min. read)

Here’s the initial app.

widget

To capture the user’s input as they type, our input element needs an event listener.

Your src/index.js file is already hooked up and ready to go. You’ll notice we imported Bootstrap for styling.

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Let’s add a dummy event listener to get things going.

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import 'bootstrap/dist/css/bootstrap.min.css';
const inputElement = document.querySelector('input');
inputElement.addEventListener('keyup', console.log);

This console.logs whatever you type. You can find the logs in DevTools of course.

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You probably know that the standard way to access an input's value is through event.target.value. Let’s edit the event handler to log it out.

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import 'bootstrap/dist/css/bootstrap.min.css';
const inputElement = document.querySelector('input');
inputElement.addEventListener('keyup', event => {
  console.log('value:', event.target.value);
});

Now it shows the value.

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How can Ramda help us achieve the following?

  • Grab event.target.value
  • Trim the output (strip leading/trailing whitespace)
  • Default to empty string if undefined

The pathOr function can actually handle the first and third bullet points. It takes three parameters: the default, the path, and the data.

So the following works perfectly

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import { pathOr } from 'ramda';
const getInputValue = pathOr('', ['target', 'value']);

If event.target.value is undefined, we’ll get an empty string back!

Ramda also has a trim function, so that solves our whitespace issue.

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import { pathOr, trim } from 'ramda';
const getInputValue = (event) => trim(pathOr('', ['target', 'value'], event));

Oh come on, we know better…let’s combine them with pipe!

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import { pathOr, pipe, trim } from 'ramda';
const getInputValue = pipe(
  pathOr('', ['target', 'value']),
  trim
);

We now have a mini pipeline that takes an event object, grabs its target.value, defaults to '', and trims it.

Beautiful.

I recommend storing this in a separate file.

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index.js
getInputValue.js
import { pathOr, pipe, trim } from 'ramda';
export default pipe(
  pathOr('', ['target', 'value']),
  trim
);