我想通过 javascript 中的两个 arrays 循环推送第三个数组中的唯一元素

Question

I tried using techniques below but did not get the desired result, is there anyone willing to share their knowledge? It would appreciated:)

for (let i = 0; i < categories.length; i++) {
  for (let j = 0; j < categories[i].features.length - 1; j++) {
    if (categories[i].features[j] !== categories[i].features[j+ 1]) {
      newCataegories.push(categories[i].features[j]);
      console.log(categories[i].features[j].id, j);
    }

  }
}
categories.forEach((element, index) => {
  element.features.forEach((e, i) => {
    if (newCataegories.indexOf(e) === -1) {
      newCataegories.push(e);
    }
  });
});

Answer 1

You can use Array.filter and Array.includes like so:

const array1 = ["a", "b", "c", "d"]
const array2 = ["a", "c"]

// Filter the array by making sure the item isn't in array 2
const array3 = array1.filter((item) => !array2.includes(item))

console.log(array3) // ["b", "d"]

Edit: const declarations (facepalm)

Answer 2

You could put the values in a Set. In fact you can use the Set constructor callback to feed it with all the feature values, using flatMap . Then only remains to convert that set to an Array (if that is what you need):

let result = Array.from(new Set(categories.flatMap(({features}) => features)));