Editing De Casteljau's algorithm (section)

=== Code Example in JavaScript ===
The following JavaScript function applies De Casteljau's algorithm to an array of control points or [https://www.sciencedirect.com/science/article/pii/S0167839624000128 poles] as originally named by De Casteljau to reduce them one by one until reaching a point in the curve for a given t between 0 for the first point of the curve and 1 for the last one

<syntaxhighlight lang="javascript" line>
function crlPtReduceDeCasteljau(points, t) {
    let retArr = [ points.slice () ];
	while (points.length > 1) {
        let midpoints = [];
		for (let i = 0; i+1 < points.length; ++i) {
			let ax = points[i][0];
			let ay = points[i][1];
			let bx = points[i+1][0];
			let by = points[i+1][1];
            // a * (1-t) + b * t = a + (b - a) * t
			midpoints.push([
				ax + (bx - ax) * t,
				ay + (by - ay) * t,
			]);
		}
        retArr.push (midpoints)
		points = midpoints;
	}
	return retArr;
}
</syntaxhighlight>

For example,

        var poles = [ [0, 128], [128, 0], [256, 0], [384, 128] ] 
        crlPtReduceDeCasteljau (poles, .5)

returns the array

        [ [ [0, 128], [128, 0], [256, 0], [384, 128 ] ], 
          [ [64, 64], [192, 0], [320, 64] ], 
          [ [128, 32], [256, 32]], 
          [ [192, 32]], 
        ]

which yields the points and segments plotted below:

[[File:Recursive Linear Interpolation.svg|center|Intermediate line segments obtained by recursively applying linear interpolation to adjacent points.]]