Closures in Javascript to create a mini DSL to filter arrays.

javascript-closures-filter-dsl

var _some = Array.prototype.some;
var _every = Array.prototype.every;

function lessThan(x){
    return function(y){
        return y < x;
    };
}
function greaterThan(x){
    return function(y){
        return y > x;
    };
}
function equalTo(x){
    return function(y){
        return x === y;
    }
}

function or(){
    var arr = arguments;
    return function(x){
        return _some.call(
            arr , function(fn){
                return fn(x);
            }
        );
    };
}

function and(){
    var arr = arguments;
    return function(x){
        return _every.call(
            arr , function(fn){
                return fn(x);
            }
        );
    };

}


//USAGE EXAMPLES
[1,2,3,1,3].filter(
    or(lessThan(3),
       greaterThan(1)));
       
[1,2,3,4,5].filter(
    and(greaterThan(2),
        lessThan(4)));