Question

我想要比较两个数组，如果第一个数组中没有它们，则只将一个数组的值添加到另一个数组中。

我写了这个函数：

class Menu {
    constructor(option, name, ingredients) {
        this.option = option;
        this.name = name;
        this.ingredients = [];
    }

    addIngredient(...ingredient) {
      for (var i = 0; i < this.ingredients.length; i++) {
        for (var j = 0; ingredient.length; j++) {
          if (this.ingredients[i] == ingredient[j]) {
            console.log(`The reciple already includes ${ingredient[j]}`);
          } else {
            this.ingredients = this.ingredients.push(ingredient[j]);
            console.log(`${ingredient[j]} has been added`);
          }
        }
      }
    }
 }

if语句的第一部分正常工作，但是当它是第二种情况时，它返回undefined。我做错了什么？

Answer 1

function mergeArrays(arr1, arr2) {
    arr2.forEach(function(el){
        if (arr1.indexOf(el) == -1) {
            arr1.push(el);
        }
    })
}

函数修改arr1

Answer 2

可能你没有初学这个成分

this.ingredients : any = [];

在推送元素之前，检查它是否为空。您还缺少console.log中的 ]

 for (var j = 0; ingredient.length; j++) {
          if (this.ingredients[i] == ingredient[j]) {
            console.log(`The reciple already includes ${ingredient[j]}`);
          } else {
            this.ingredients.push(ingredient[j]);
            console.log(`${ingredient[j]} has been added`);
          }
        }

<强> EDIT

替换行，

this.ingredients = this.ingredients.push(ingredient[j]);

与

this.ingredients.push(ingredient[j]);

Answer 3

您需要检查元素是否存在。这里不需要循环，indexOf将起作用。然后push您的参赛作品。 push不会返回数组。

class Menu {
  constructor(option, name, ingredients) {
    this.option = option;
    this.name = name;
    this.ingredients = [];
  }

  addIngredient(...ingredient) {
    for (var i = 0; i < ingredient.length; i++) {
      if (this.ingredients.indexOf(ingredient[i]) == -1) {
        this.ingredients.push(ingredient[i]);
        console.log(`${ingredient[i]} has been added`);
      } else {
        console.log(`The reciple already includes ${ingredient[i]}`);
        
      }
    }
  }

}

//lets test
var a = new Menu("Test", "test");
a.addIngredient("a", "b", "c", "a");

使用Andrea的功能：

class Menu {
  constructor(option, name, ingredients) {
    this.option = option;
    this.name = name;
    this.ingredients = [];
  }

  addIngredient(...ingredient) {
    mergeArrays(this.ingredients, ingredient);
  }

}

function mergeArrays(arr1, arr2) {
    arr2.forEach((el) => {
        if (arr1.indexOf(el) == -1) {
            arr1.push(el);
        }
        else
        {
          console.log(`"${el}" already exists in the array.`) //debugging only
        }
    })
}

//lets test
var a = new Menu("Test", "test");
a.addIngredient("a", "b", "c", "a");

如果else for double for循环返回undefined

3 个答案: