javascript storing for loop result

Question

Is there a way to store the result of the 'for loop' in a variable?

I want to display the two name kevin and elsa in a div for example.

I know i can do john.friends[0].nom, john.friends[1].nom;

but if John has many friends, it will be difficult...

Now the variable friendName gives me just name, I understand why but can't see the solution...

Thanks !

function Person(name, age, friends) {
    this.name = name;
    this.age = age;
    this.friends = friends;

};

var john = new Person('john', 28, [new Person('elsa', 29, []), new Person('kevin', 31, [])]);

for (var i = 0; i < john.friends.length; i++) {
    var friendName = john.friends[i].name;
}

alert(friendName);

I'd ask what exactly are you trying to accomplish? Since you can get john's friends by calling john.friends, just having another variable pointing to those friends is redundant. — zeh
– zeh, Commented Jul 12, 2012 at 15:42

Daniel Li · Accepted Answer · 2012-07-12 15:40:48Z

6

var friendNames = []; // store their names within a local array

for(var i = 0; i < john.friends.length; i++){
    friendNames.push(john.friends[i].name);
}

console.log(friendNames); // log to the browser (readability) instead of alert

answered Jul 12, 2012 at 15:40

Daniel Li

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1 Comment

Elliot Bonneville Over a year ago

That is exactly what I just answered, down to the variable names and log call. The question is... by coincidence or design?

Elliot Bonneville · Accepted Answer · 2012-07-12 15:40:39Z

2

var friendNames = []; // create array to hold friend names

for(var i=0; i < john.friends.length; i++){    
    friendNames.push(john.friends[i].name); // add friend's name to the array
}

console.log(friendNames); // an array containing all of John's friends' names.

answered Jul 12, 2012 at 15:40

Elliot Bonneville

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Comments

Raekye · Accepted Answer · 2012-07-12 15:49:32Z

You probably want an array of names (list of all the names). Declare friendName = new Array() and friendName.push(john.friends[i].name);

var friendName = new Array();
for (var i = 0; i < john.friends.length; i++) {
    friendName.push(john.friends[i].name);
    //or friendName[i] = john.friends[i].name;
}
//friendName is now an array of names. Use it as you need (the last line is useful for debugging)
for (i = 0; i < friendName.length; i++) alert(friendName[i]);

The problem with your old code was that each iteration of the loop would reassign friendName. When i = 0, 'elsa' was assigned to friendName. When i = 1, 'kevin' was reassigned to friendName.

Furthermore, javascript does not have block scoping; it would be like calling var friendName = 'elsa'; var friendName = 'kevin';. Won't crap out the javascript engine, but just watch out for that. Better to declare friendName as an array above the loop as others and I have mentioned.

Rich O'Kelly · Accepted Answer · 2012-07-13 12:31:28Z

1

Since your friends variable is an array, you can just use some of the methods available to you on that type:

var friendString = john.friends.map(function(f) { return f.name; }).join(' ');

In the above example, the map method maps the friends to just their names and then the join method will produce a space separated string of all johns friends.

edited Jul 13, 2012 at 12:31

answered Jul 12, 2012 at 15:40

Rich O'Kelly

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2 Comments

user1521149 Over a year ago

Mmmmm i don't understand the map method return me an array like this: ["",""]

Rich O'Kelly Over a year ago

@user1521149 Answer updated - I didn't include the argument in the callback. Apologies.

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