Extend algorithm that based on loop

Question

my algorithm computes a path through the DOM. It starts with the given component and goes up the tree. Each time a parent component has a specific attribute, the algorithm adds its value to the path.

_computePath(aComponent) {
  let result = '';
  let parent = aComponent.parentNode;

  while (parent.tagName !== 'MY-ROOT-COMPONENT') {
    if (parent.hasAttribute('my-attribute')) {
      result = `/${parent.getAttribute('my-attribute')}${result}`;
    }
    parent = parent.parentNode;
  }

  return result;
}

In an other part of my application, i need a slightly different version.

_computePath(aComponent) {
  let result = '';
  let parent = aComponent.parentNode;

  while (parent.tagName !== 'MY-ROOT-COMPONENT') {
    if (parent.tagName === 'SPECIAL-COMPONENT') {
      result = null;
      break;
    }

    if (parent.condition === 'special') {
      result = null;
      break;
    }

    if (parent.hasAttribute('my-attribute')) {
      result = `/${parent.getAttribute('my-attribute')}${result}`;
    }
    parent = parent.parentNode;
  }

  return result;
}

How can i extend the algorithm of the first loop, without repeat the code?

There is probably a very simple solution, but somehow I can't figure it out.

Thank you

Barmar · Accepted Answer · 2020-12-11 06:53:53Z

1

Have the function take a callback that tests for the conditions that cause it to break.

_computePath(aComponent, stopfun = parent => false) {
  let result = '';
  let parent = aComponent.parentNode;

  while (parent.tagName !== 'MY-ROOT-COMPONENT') {
    if (stopfun(parent)) {
      result = null;
      break;
    }

    if (parent.hasAttribute('my-attribute')) {
      result = `/${parent.getAttribute('my-attribute')}${result}`;
    }
    parent = parent.parentNode;
  }

  return result;
}

let result1 = obj1._computePath(component1); // no extra stop check
let result2 = obj2._computePath(component2, parent => parent.tagName === 'SPECIAL-COMPONENT' || parent.condition === 'special');

answered Dec 11, 2020 at 6:53

Barmar

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3 Comments

Meisenmann Over a year ago

Thank you for your answer. This was also my first thought. But i'm not sure if its too "dangerous" to pass a reference variable that is modified by a loop to a function?

Barmar Over a year ago

The variable isn't modified by the function. That's the default value of the parameter, it doesn't modify the caller's variable.

Barmar Over a year ago

JavaScript doesn't pass variables by reference.

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