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71

Is there an indexOf in javascript to search an array with custom compare function

rated 0 times [ 76] [ 5] / answers: 1 / hits: 32976 / 12 Years ago, mon, september 10, 2012, 12:00:00

I need the index of the first value in the array, that matches a custom compare function.

The very nice underscorej has a find function that returns the first value where a function returns true, but I would need this that returns the index instead. Is there a version of indexOf available somewhere, where I can pass a function used to comparing?

Thanks for any suggestions!

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julissaimana

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2 Years ago

answered 12 Years ago zaynerogerb · Accepted Answer

Here's the Underscore way to do it - this augments the core Underscore function with one that accepts an iterator function:

// save a reference to the core implementation

var indexOfValue = _.indexOf;



// using .mixin allows both wrapped and unwrapped calls:

// _(array).indexOf(...) and _.indexOf(array, ...)

_.mixin({



    // return the index of the first array element passing a test

    indexOf: function(array, test) {

        // delegate to standard indexOf if the test isn't a function

        if (!_.isFunction(test)) return indexOfValue(array, test);

        // otherwise, look for the index

        for (var x = 0; x < array.length; x++) {

            if (test(array[x])) return x;

        }

        // not found, return fail value

        return -1;

    }



});



_.indexOf([1,2,3], 3); // 2

_.indexOf([1,2,3], function(el) { return el > 2; } ); // 2