What is the use of e in this code? Also how is this.add preventing duplicate values

Curriculum Help JavaScript
#1

function mySet(){

var collection = [];

this.has = function(element){

    return (collection.indexOf(element) !== -1)

}

this.values = function(){

    return collection;

}

this.add = function(element){

    if(!this.has(element)){

        collection.push(element);

        return true;

    }

this.remove = function(element){

    if(this.has(element)){

        index = collection.indexOf(element);

        collection.splice(index, 1);

        return true;

    }

    return false;

}

this.size = function(){

    return collection.length;

}

this.union = function(otherSet){

    var unionSet = new Set();

    var firstSet = this.values();

    var secondSet = otherSet.values();

    firstSet.forEach(function(e){

        unionSet.add(e);

    })

    secondSet.forEach(function(e){

        unionSet.add(e);

    })

    return unionSet;

}

this.difference = function(otherSeet){

    var differenceSet = new mySet();

    var firstSet = this.values();

    firstSet.forEach(function(e){

        if(!otherSet.has(e)){

            differenceSet.add(e)

        }

        return differenceSet;

    })

    this.subset = function(otherSet){

        var firstSet = this.values();

        return firstSet.every(function(value){

            return otherSet.has(value);

        })

    }

}

}

}

#2

e in this code is being used as an event parameter. It is essentially holding an object containing the events that happened to the target.

#3

Regarding forEach, check this link..

function(e) means that e is the argument to the function, the thing that the function takes in and acts upon.

In the case of forEach(fucntion(e){})the function specified in the brackets is going to act on (take as an argument) e, but e here is just kind of a dummy variable representing every item in the array (the forEach will do the function once on each entry of the array). Again, see the linked example if unclear.

1 Like