Question 265269 in Html Question posted in
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Html – Array stores duplicate elements even after excluding them

I try to dynamically add elements to an Array. If the element in the Array exists, skip it, if it does not exist, add it. The console.log within the .map() function shows, that values have been added. However, it adds too many.

recipes.js

const getUniqueTags = async (req,res)=>{
    const allRecipes = await Recipe.find({}).select("tag");
    let resultArray =[];
    resultArray = allRecipes.map( recipe =>{
        const tag = recipe.tag;
        if(resultArray.includes(tag)){
            
        }
        else{
            return tag;
        }
    });

    console.log(resultArray);
    res.status(200).json(resultArray)
}

console.log

[ Breakfast, Lunch, Lunch, Breakfast ]

What am I doing wrong? Includes does not work, neither does new Set()

Tags:

2

Answers


  1. 0

    You’re not updating resultArray during the map() loop. So resultArray.includes(tag) is always false, so you do return tag every time.

    Use a Set instead of an array, it automatically removes duplicates.

    let resultSet = new Set(allRecipes.map(r => r.tag));

    If you want an array, you can convert it at the end:

    let resultArray = [...resultSet];

    const allRecipes = [{
  tag: "Breakfast"
}, {
  tag: "Lunch",
}, {
  tag: "Dinner",
}, {
  tag: "Breakfast"
}];

let resultSet = new Set(allRecipes.map(r => r.tag));
let resultArray = [...resultSet];
console.log(resultArray);
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  2. 0

    For Simple array you can use

    const uniqueArray=[...new Set(array)];

    for Array of objects

    const uniqueArray = array.filter((item, index) => {
     return index === array.findIndex(obj => obj['key'] === item['key'])
});
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