javascript - 我怎样才能从中获得特定的 key ？

Question

我过去使用过 hasOwnProperty 和 typeof 但这个难倒了我......我正在尝试获取所有具有匹配键的键，以便我可以将它们与其他键配对示例:

{"meals": [{    
  strIngredient1  : lemons
  strIngredient2    :   paprika
  strIngredient3    :   red onions
  strIngredient4    :   chicken thighs
  strIngredient5    :   vegetable oil
  strMeasure1   :   2 Juice
  strMeasure2   :   4 tsp
  strMeasure3   :   2 finely chopped
  strMeasure4   :   16 skinnless
  strMeasure5   :   
}]}

很明显，strIngredient1 与 strMeasure1 等匹配......任何建议或帮助将不胜感激!

Answer 1

解释

在此示例中，您可以看到我分两部分提供了解决方案，一个是从膳食数组中简单访问 'x' 成分的简单方法，然后是另一个解决方案将迭代一系列膳食，打印出每种成分。

正如我在解决方案中所述，您可以使用 forEach 或者，您也可以使用 map 或 reduce 等函数如果你希望。如果您不知道何时使用哪个，基本经验法则是，如果满足以下条件，您将使用 map 或 reduce您希望遵循函数式编程概念。 forEach 解决方案允许更容易发生副作用等...我的意思是这在一定程度上是有争议的，但无论如何这是基本思想...

编辑

我为这个演示添加了一个简单的日志功能，长话短说，当你运行这个代码片段时，我个人觉得控制台窗口提供的空间太少了，这很恶心，所以在之后一次记录一件事一些延迟并清除控制台。

let delay = 0;
const DELAY_INC = 1500;

// Just for this demo, have the ability to log something, 
// after a delay and clear the console.
const log = (arg, alrt) => {
  setTimeout(() => {
    console.clear();
    console.log(arg);
    if (alrt != null) {
      alert(alrt);
    }
  }, delay);
  delay += DELAY_INC;
};

// Your data.
var data = {
  "meals": [{
    strIngredient1: 'lemons',
    strIngredient2: 'paprika',
    strIngredient3: 'red onions',
    strIngredient4: 'chicken thighs',
    strIngredient5: 'vegetable oil',
    strMeasure1: '2 Juice',
    strMeasure2: '4 tsp',
    strMeasure3: '2 finely chopped',
    strMeasure4: '16 skinnless',
    strMeasure5: ''
  }]
};

// Just some demo.
var meals = data.meals;
var meal = meals[0];
var ingredient = meal.strIngredient1;

log(data); // Log the raw data.
log(meals); // Log the array of meals.
log(meal); // Log a specific meal.
log(ingredient); // Log a specific ingredient.

// If you wish to iterate, log each ingredient for each meal. 
data.meals.forEach(meal => Object.keys(meal).forEach(key => log(meal[key])));

// Here's a solution.
const newArray = data.meals.reduce((array, meal) => {
  // Rather than iterate over ALL of the keys, just 
  // do this, basically 50% of the keys. 
  const subArray = Object.keys(meal).filter(key => key.indexOf('strIngredient' == -1));

  // Basically add some ojects to the array.
  subArray.forEach(key => {
    const int = key.replace(/\D/g, '');
    const measureKey = `strMeasure${int}`;
    const ingredientKey = `strIngredient${int}`;

    const obj = {
      ingredient: meal[ingredientKey],
      measure: meal[measureKey]
    };

    array.push(obj);
  });

  // Make sure to return the array.
  return array;
}, []);

// Now just print the resuts, and make sure that you know 
// and alert that the app has finished. 
log(newArray, 'FINISHED');