Hello.

After a while I managed to make the function composition work for task 3 of Coordinate Transformation in JavaScript on Exercism

But for some reason my program doesn’t pass tests 10 and 11:

composeTransform > should compose in the correct order: g(f(x))

composeTransform > should compose in the opposite order: f(g(x))

But I have no idea why because my function seems to work when I try it manually, regardless of the order of the composition.

Maybe there’s something I’m not understanding.

Could anybody help me?

Thanks.

The following is my code with my three functions in it:

```
export function translate2d(dx, dy) {
let translate = [dx,dy];
function updateTranslate(a, b) {
translate[0] = translate[0] + a;
translate[1] = translate[1] + b;
return translate;
}
return updateTranslate;
}
/**
* Create a function that returns a function making use of a closure to
* perform a repeatable 2d scale of a coordinate pair.
*
* @param {number} sx the amount to scale the x component
* @param {number} sy the amount to scale the y component
*
* @returns {function} a function which takes an x, y parameter, returns the
* scaled coordinate pair in the form [x, y]
*/
export function scale2d(sx, sy) {
let scale = [sx, sy];
function updateScale(a, b) {
scale[0] = scale[0] * a;
scale[1] = scale[1] * b;
return scale;
}
return updateScale;
}
/**
* Create a composition function that returns a function that combines two
* functions to perform a repeatable transformation
*
* @param {function} f the first function to apply
* @param {function} g the second function to apply
*
* @returns {function} a function which takes an x, y parameter, returns the
* transformed coordinate pair in the form [x, y]
*/
export function composeTransform(f, g) {
/**let firstTransform = f;
let secondTransform = g;**/
function performComposition(a, b) {
/**let firstStep = f(a,b);
let result = g(f(a,b)[0], f(a,b)[1])**/
return g(f(a,b)[0], f(a,b)[1]);
}
return performComposition;
}
```