clamp.js

clamp.js

function clamp(min, max, mid){
	if (min <= max) { // Sanity check

		if (mid > max) {
			// Also implied: mid is not NaN
			return max;
		}

		if (mid < min) {
			// Also implied: mid is not NaN
			return min;
		}

		// At this point mid is either between min and max or it's NaN.
		// Both cases are okay, we just return what we have.
		return mid;

	} else {
		// Oops! max is less than min.
		// Or worse: min or max (or both) is NaN
		return NaN;
	}
}

// Does this func look too verbose?
// We'll anyway pass it through the minifier in the production build.
// And afther the uglifyjs we'll get this:

// function clamp(n,a,c){return a>=n?c>a?a:n>c?n:c:NaN}

// Minifiers are pretty smart nowadays!


// You may wonder why I've change the signature
// from (min, mid, max)
// to   (min, max, mid).

// That may look like a strange decision, but look what we can do now.
// Partial applications!

var zeroToOneClamp = clamp.bind(null, 0, 1);
zeroToOneClamp(42); // 1
zeroToOneClamp(0.5); // 0.5
zeroToOneClamp(-42); // 0