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/**
 *  remove the repeat element in an array of Objects
 * 
 * @param {Array} originalArray - original Array
 * @param {String} [prop=undefined] - optional, if this field has set and vaild,
 *  then the function will remove repeat by the appointed key, else remove
 *  repeat by all keys
 * @returns {Array} - new Array
 */

function removeRepeat(originalArray, prop) {
    // type checker
    if (originalArray && (originalArray instanceof Array)) {
        if (originalArray.length <= 1) {
            return originalArray;
        }

        let newArray = [];

        // type checker
        if (prop && (typeof prop === 'string')) {

            // check if the prop is vaild
            if (Object.keys(originalArray[0])
                .includes(prop)) {
                let repeatKiller = {};

                // use the feature of Object[no repeat key] to remove repeat array element
                originalArray.forEach(function(el) {
                    repeatKiller[el[prop]] = el;
                });

                // put the values of repeatKiller Object to the newArray
                Object.keys(repeatKiller)
                    .forEach(function(el) {
                        newArray.push(repeatKiller[el]);
                    });
            } else {
                newArray = [...new Set(originalArray.map(JSON.stringify))].map(JSON.parse)
            }
        } else {
            newArray = [...new Set(originalArray.map(JSON.stringify))].map(JSON.parse)
        }

        // return the newArray
        return newArray;
    }
}

// array of Objects
let shops = [{
    shopName: "shop 1",
    id: 1000
}, {
    shopName: "shop 21",
    id: 1001
}, {
    shopName: "shop 21",
    id: 1002
}, {
    shopName: "shop 1",
    id: 1000
}, {
    shopName: "shop 41",
    id: 1004
}, {
    shopName: "shop 1",
    id: 1005
}, {
    shopName: "shop 61",
    id: 1006
}];

// tests
console.log(removeRepeat(shops.slice(0, 1))) // array(length<=1)
console.log('\n')
console.log(removeRepeat(shops)) // array(length>1)
console.log('\n')
console.log(removeRepeat(shops, 'shopName')) // has vaild prop
console.log('\n')
console.log(removeRepeat(shops, 'invalidKey')) // invalid prop
console.log('\n')
console.log(removeRepeat(shops, ['shopName'])) // invalid prop
console.log('\n')
console.log(removeRepeat(shops[0])) // invaild array