在树状结构中查找具有属性的第一个对象

Question

I have a structure like this:

[{
  description: 'Beef Stew',
  complete: false,
  tasks: [{
    description: 'Cut vegetables',
    complete: false,
    tasks: [{
      description: 'Dice carrots',
      complete: false
    }, {
      description: 'Mince Garlic',
      complete: false
    }, {
      description: 'Prepare potatoes',
      complete: false,
      tasks: [{
        description: 'Peel potatoes',
        complete: false
      }, {
        description: 'Cut potatoes',
        complete: false
      }]
    }]
  }]
}]

In this case, I am looking for the first occurance of an element with no tasks that is not complete . In this case, that means it should be { description: 'Dice carrots', completed: false } . Here is the basic of what I have written. codepen here too .

function next(steps) {
  return steps.reduce((r, step) => {
    return (step.tasks && step.tasks.length > 0 && !step.complete) ? next(step.tasks) : step;
  }, []);
}

This does get a deep step, but it ends up getting the last step. How can I make an algorithm that will get the first?

Answer 1

I would use Array.prototype.find()

The mozilla site provides a polyfill implementation of this.

Applying it to your problem:

var matchingStep = steps.find(function(step) {
    return !(step.tasks.find(function(task) { return !(task.complete); });
});

Answer 2

I got a pretty good solution in my Steps class, for if anyone is looking for the answer in the future.

class Steps {
  constructor(steps) {
    this.steps = steps;
    this.current = steps;
  }
  next(steps=this.steps) {
    for(let step of steps) {
      if (step.tasks instanceof Array && !step.complete) {
        return this.next(step.tasks);
      }
      return this.current = step;
    }
  }
}

This allows me to advance the step forward recursively.