loop though an array and return a set of array index's values concatenated in one variable

Question

The question it's not so relevant but what I want to achieve is the next :

var some_array = [Modernizr.json, Modernizr.csstransforms];

var tests = function() {
    for (var i = some_array .length - 1; i >= 0; i--) {
       ...
    };

    return  Modernizr.json && Modernizr.csstransforms;
};

I keep thinking of the logic that would do what I tried to show you, but I cannot figure it out. Basically I need to loop the array of tests and return a boolean operation between the tests, to be more specific I want to take the array [Modernizr.json, Modernizr.csstransforms] and I want to return Modernizr.json && Modernizr.csstransforms and so on ( if there are more values in the array ).

I don't know tbh. In it's current state I have no idea what it is you are looking for. Could you please clarify your question? — PeeHaa
– PeeHaa, Commented Oct 21, 2012 at 13:02
I don't think so ... is it so hard to understand ? I want to get from an array to an boolean operation ( && ) between the array values ... isn't this clear enough ? because I have no idea how to explain this in any other way (: — Roland
– Roland, Commented Oct 21, 2012 at 13:23

Bergi · Accepted Answer · 2012-10-21 13:35:21Z

1

Use reduce:

return some_array.reduce(function(a, b){ return a && b; });

or reduceRight if you want to iterate backwards.

If you want to break the loop once a falsy value is encountered, you also could use every.

answered Oct 21, 2012 at 13:35

Bergi

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3 Comments

pckill Over a year ago

reduce is not supported in IE8 and lower

Roland Over a year ago

and what if I have more than two values, what if there are 15 ? will the above statement still work ?

Bergi Over a year ago

@Roland: some_array can be an array of any length (should be at least 2 for reducing)

pckill · Accepted Answer · 2012-10-21 13:24:43Z

1

If you want to check if all values in your array are true, you can do this:

var some_array = [Modernizr.json, Modernizr.csstransforms];

var tests = function() {
    var result = true;
    for (var i = some_array .length - 1; i >= 0; i--) {
        result = result && some_array[i];
    };
    return result;
};

answered Oct 21, 2012 at 13:24

pckill

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Comments

Roland · Accepted Answer · 2012-10-21 14:03:53Z

0

I found a good solution for what I was looking for, based on @Bergi's answer :

some_array.reduce(function(previousValue, currentValue, index, array){
    return previousValue && currentValue;
});

answered Oct 21, 2012 at 14:03

Roland

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1 Comment

Bergi Over a year ago

Yes, that's exactly my solution…

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