Question

In javascript I need to know if array contains value. Values are objects and I can have different instances of same object, which means $.inArray(…) will not work. I know how to do my task using $.each(…) and my question is – is it possible to pass function with value’s comparing logic to any of jQuery methods (see sample with desired sintax)?

    // values
var val1 = { id: 1, description: 'First value'};
var val2 = { id: 2, description: 'Second value'};
var val3 = { id: 3, description: 'Third value'};        
// array of values
var values = [ val1, val2, val3 ];
// inArray of jQuery to know if value is in array -> returns TRUE
var isInArray = $.inArray(val2, values) > -1;

// another instance of same object "val2"
var val2_anotherInstance = { id: 2, description: 'Second value'};
// inArray works as expected -> returns FALSE but desirable result is TRUE
var isInArray_anotherInstance = $.inArray(val2_anotherInstance, values) > -1;

// define function for comparing values (any logic can be implemented, for example searching by Id)
var valueComparer = function(first, second) {
    return first.id == second.id && first.description == second.description;
}
// function compares objects and returns true for different instances
alert(valueComparer(val2, val2_anotherInstance));

// desirable sintax:
// is something like this possible ???      
// NOTE next line not correct
isInArray_anotherInstance = $.inArray(val2_anotherInstance, values, valueComparer) > -1;
// actually what I want is specify criteria for searching value in array

Answer 1

Try grep:

var val1 = { id: 1, description: 'First value'};
var val2 = { id: 2, description: 'Second value'};
var val3 = { id: 3, description: 'Third value'};        

var values = [ val1, val2, val3 ];

// another instance of same object "val2"
var val2_anotherInstance = { id: 2, description: 'Second value'};


var items = $.grep(values, function(x) {
    return x.id == val2_anotherInstance.id
})

var found = items.length > 0

For more elegance, you can use a boolean aggregator function, as provided in this answer:

val2_in_array = $.some(values, function() {
    return this.id == val2_anotherInstance.id
});