Detect duplicate object properties in JavaScript

Question

Based on a quick mockup like below I need to add URL route objects to an Array property in my app.

in the function below addAppRoute(routeObbj) I would like to add a check to see if the new route being added already exist or not in the property this.cache.webDevAppRoutes

How can I make sure duplicates are not added? It would need to be based on a duplicate module and action being the same

var app = {
    cache: {
        webDevAppRoutes: [],
    },

    addAppRoute: function(route) {
        var routes = this.cache.webDevAppRoutes;
        routes.push(route);
    },

    getAppRoutes: function() {
        var routes = this.cache.webDevAppRoutes;
        console.log(routes);
    },

    addBookmarkAppRoutes: function() {

        this.addAppRoute({
            module: 'bookmarks',
            action: 'view',
            params: [{
                id: 123
            }],
        });

        this.addAppRoute({
            module: 'bookmarks',
            action: 'edit',
            params: [{
                id: 123
            }],
        });

        this.addAppRoute({
            module: 'bookmarks',
            action: 'add',
            params: [],
        });
    },

}

T.J. Crowder · Accepted Answer · 2016-11-24 08:33:34Z

2

Just loop through the array and check that it doesn't already have an entry with that module and action. You can use Array#some, for instance:

if (routes.some(function(r) { return r.module == route.module && r.action == route.action)) {
    // It's a duplicate
}

Array#some returns true as soon as a call to its callback returns a truthy value; otherwise, it returns false.

In ES2015, that's a bit more concise:

if (routes.some(r => r.module == route.module && r.action == route.action)) {
    // It's a duplicate
}

answered Nov 24, 2016 at 8:33

T.J. Crowder

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Comments

georg · Accepted Answer · 2016-11-24 08:41:05Z

1

Just have a Map of already added routes:

var webDevAppRoutes = new Map();


function addAppRoute(route) {
    var key = [route.module, route.action].join();

    if(!webDevAppRoutes.has(key))
        webDevAppRoutes.set(key, route);
}

addAppRoute({
    module: 'bookmarks',
    action: 'view',
    params: [{
        id: 123
    }],
});

addAppRoute({
    module: 'bookmarks',
    action: 'edit',
    params: [{
        id: 123
    }],
});

addAppRoute({
    module: 'bookmarks',
    action: 'add',
    params: [],
});

addAppRoute({
    module: 'bookmarks',
    action: 'add',
    params: 'once again',
});

console.log([...webDevAppRoutes.values()])

For ES5, find a polyfill or use a POJO instead of Map.

answered Nov 24, 2016 at 8:41

georg

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2 Comments

JasonDavis Over a year ago

This is interesting and nice to see a new feature example usage. I notice that var webDevAppRoutes no longer behaves like an array of objects. Is there a way to use this to prevent duplicate routes being added to my array while still allowing me to access my object property as an array of objects?

georg Over a year ago

@JasonDavis: look at the last line: map.values() gives you an iterator, and [...map.values()] is a normal array.

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