數組對象去重

數組對象去重

• 方法1：利用對象訪問屬性的方法，判斷對象中是否存在key、value

const arr = [
    {
        key: "1",
        value: "西瓜"
    },
    {
        key: "1",
        value: "蘋果"
    },
    {
        key: "3",
        value: "桃子"
    }
];
const list = [
    {
        key: "1",
        value: "哈密瓜"
    },
    {
        key: "2",
        value: "黃瓜"
    },
    {
        key: "3",
        value: "黃瓜"
    }
];


function  unique (obj1,obj2,targe) {
    const data = []; // 建立一個新數組
    const obj = {}; // 建立一個新對象
    const list = obj1.concat(obj2);
    for (let i=0; i< list.length; i++) {
        if (!obj[list[i][targe]]) { // 判斷對象不存在key、value
            data.push(list[i]);
            obj[list[i][targe]] = true;
        }
    }
    return data;
}        
console.log( unique(arr, list, "value"));
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• 方法2：利用reduce方法遍歷數組,reduce第一個參數是遍歷須要執行的函數，第二個參數是item的初始值

const arr = [
    {
        key: "1",
        value: "西瓜"
    },
    {
        key: "1",
        value: "蘋果"
    },
    {
        key: "3",
        value: "桃子"
    }
];
const list = [
    {
        key: "1",
        value: "哈密瓜"
    },
    {
        key: "2",
        value: "黃瓜"
    },
    {
        key: "3",
        value: "黃瓜"
    }
];




function  unique (obj1,obj2,targe) {
    const obj = {}; // 建立一個新對象
    const list = obj1.concat(obj2);
    const data = list.reduce(function(item,next) {
        if (!obj[next[targe]]) {
            item.push(next)
            obj[next[targe]] = true;
        }
        return item;
    }, []);
    return data;
}        
console.log(unique(arr, list, "value"));
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• 方法3：利用Map的特性去重

const arr = [
    {
        key: "1",
        value: "西瓜"
    },
    {
        key: "1",
        value: "蘋果"
    },
    {
        key: "3",
        value: "桃子"
    }
];
const list = [
    {
        key: "1",
        value: "哈密瓜"
    },
    {
        key: "2",
        value: "黃瓜"
    },
    {
        key: "3",
        value: "黃瓜"
    }
];


 function unique(obj1,obj2,targe) {
    const data = [...obj1, ...obj2];
    const res = new Map();
    return data.filter((value) => {
       return !res.has(value[targe]) && res.set(value[targe], 1)
    } )
}          
console.log(unique(arr, list, "value"));
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