Typescript/Javascript Call Method Reference with arguments

Question

I have a bulk operation that operates on a 2 dimensional array. It shall call a given method "func" on each element in the array:

function forEachMatrixElement(matrix: Complex[][], func: Function): Complex[][] {
  let matrixResult: Complex[][] = new Array(countRows(matrix)).fill(false).map(() => new Array(countCols(matrix)).fill(false)); // Creates a result 2D-Matrix
  for (let row = 0; row < countRows(matrix); row++) {
    for (let col = 0; col < countCols(matrix); col++) {
      matrixResult[row][col] = func.call(matrix[row][col]); // Call the given method
    }
  }
  return matrixResult;
}

I have two functions that I want to delegate to this method: This one takes no additional arguments and works fine:

export function conjugateMatrix(matrix: Complex[][]): Complex[][] {
  return forEachMatrixElement(matrix, Complex.prototype.conjugate);
}

This one takes an additional argument (a scalar). But I don't know how to add this argument to this method reference on the prototype:

export function multiplyMatrixScalar(matrix: Complex[][], scalar: Complex): Complex[][] {
  return forEachMatrixElement(matrix, Complex.prototype.mul); // TODO Call with scalar
}

Alex Wayne · Accepted Answer · 2022-11-21 19:43:01Z

2

Reaching into the prototype and manipulating the value of this with call() is usually a bad idea. This can be made simpler.

Instead, the forEachMatrixElement should simply take a function that accepts a Complex instance, and the caller can decide what that function does and how to apply its arguments.

For example:

function forEachMatrixElement(
  matrix: Complex[][],
  func: (complex: Complex) => Complex // Changed this function type
): Complex[][] {
  let matrixResult: Complex[][] = new Array(countRows(matrix)).fill(false).map(() => new Array(countCols(matrix)).fill(false));
  for (let row = 0; row < countRows(matrix); row++) {
    for (let col = 0; col < countCols(matrix); col++) {
     
      // just invoke the function like any other. No .call()
      matrixResult[row][col] = func(matrix[row][col]); 
      
    }
  }
  return matrixResult;
}

Now the functions that call this can simply be:

export function conjugateMatrix(matrix: Complex[][]): Complex[][] {
  return forEachMatrixElement(matrix, (c) => c.conjugate());
}

export function multiplyMatrixScalar(matrix: Complex[][], scalar: Complex): Complex[][] {
  return forEachMatrixElement(matrix, (c) => c.mul(scalar));
}

See Playground

answered Nov 21, 2022 at 19:43

Alex Wayne

188k52 gold badges328 silver badges363 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Alex Wayne Over a year ago

Also I think your forEachMatrixElement() can be much simpler with some simple map() calls. tsplay.dev/NrXJaW

Drew Pereli · Accepted Answer · 2022-11-21 19:42:59Z

2

Could you just create a new function in multiplyMatrixScalar?

Something like:

export function multiplyMatrixScalar(matrix: Complex[][], scalar: Complex): Complex[][] {
  const fn = function (this: Complex) { return this.mul(c, scalar)};

  return forEachMatrixElement(matrix, fn);
}

edited Nov 21, 2022 at 19:42

answered Nov 21, 2022 at 19:23

Drew Pereli

2541 silver badge7 bronze badges

4 Comments

Drew Pereli Over a year ago

So something like const fn = (c: Complex) => c.mul(scalar); for the function then?

Drew Pereli Over a year ago

Or I guess it would be const fn = function(this: Complex) { this.mul(scalar); } if you're using .call

Oli Over a year ago

Return is missing. But the answer is correct. Thank you. Would you like to complete it?: const fn = function(this: Complex) { return this.mul(scalar); }

Drew Pereli Over a year ago

Right you are, thank you. I'll update the answer.

David Min · Accepted Answer · 2022-11-21 19:34:20Z

0

MDN Function.call() can take additional parameters as arguments. So the first parameter will always be the this bind, the second and onwards are arguments.

Wonder if this is what will solve your issue? So your code will look like

function forEachMatrixElement(matrix: Complex[][], func: Function, scalar?: Complex)

and

func.call(matrix[row][col], scalar)

answered Nov 21, 2022 at 19:34

David Min

1,52514 silver badges35 bronze badges

1 Comment

Oli Over a year ago

I don't want to add additional arguments to forEachMatrixElement. The provided function func has to be complete

Collectives™ on Stack Overflow

Typescript/Javascript Call Method Reference with arguments

3 Answers 3

1 Comment

4 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

4 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related