A simple linear scale function generator, similar to D3's

linearScale.js

(function ( global ) {
        
	'use strict';

	var linearScale = function ( domain, range ) {
		var d0 = domain[0], r0 = range[0], multiplier = ( range[1] - r0 ) / ( domain[1] - d0 );

		// special case
		if ( r0 === range[1] ) {
			return function () {
				return r0;
			};
		}

		return function ( num ) {
			return r0 + ( multiplier * ( num - d0 ) );
		};
	};

	// export as CommonJS...
	if ( typeof module !== 'undefined' && module.exports ) {
		module.exports = linearScale;
	}

	// ...or as AMD module
	else if ( typeof define !== 'undefined' && define.amd ) {
		define( function () { return linearScale; });
	}

	// ...or as browser global
	else {
		global.linearScale = linearScale;
	}

}( this ));