Boolean shorthands and truthiness

Today in the current session of Vanilla JS Academy, my students are working on a character and word count script.

My solution for counting words looks like this.

// Split the text content into an array, using spaces to break words
// Use Array.filter() to remove any words without a length
// (this removes double spaces in the content)
let words = text.value.split(' ').filter(function (word) {
	return word.length;
});

One of my students has a solution that looks like this.

// Split the text content into an array, using spaces to break words
// Use Array.filter() to remove any words without a length
// (this removes double spaces in the content)
let words = text.value.split(' ').filter(function (word) {
	return word.length > 0;
});

They asked me why return word.length works in my Array.filter() method even though it’s not explicitly checking to see if the word.length is greater than 0.

In JavaScript, a value of 0 is considered false for truthy evaluation purposes, and a number higher than that is considered true.

Because the word.length property returns an integer, starting at 0 and going up, the Array.filter() method evaluates it as true or false automatically.

I like it because it saves me a little typing, but if you find the more explicit comparison more clear, by all means use it.