jQuery $ .inArray似乎不适用于关联数组

Question

I have made this fiddle: http://jsfiddle.net/benhowdle89/CANX8/1/

Which creates an assoc array and then runs a test for a value that is in the array. The wrong results are reached!

Outline of code:

$(document).ready(function(){
    var newArray = [];
    newArray['first'] = 1;
    newArray['second'] = 1;

    $('button').click(function(){
        if($.inArray(1, newArray) != -1){
            $('#dump').css('border', '1px solid red');
        } else {
            $('#dump').css('border', '1px solid blue');
        }
    });
});

Answer 1

var newArray = [];
newArray['first'] = 1;
newArray['second'] = 1;

This will not add any elements to the array. You can see newArray.length will be zero.

Instead it adds properties first and second to newArray .

You can access it using

newArray.first
newArray.second

So $.inArray will not work

Answer 2

The indices of a JavaScript array are unsigned 32 bit integers and therefore you can't use strings, see http://andrewdupont.net/2006/05/18/javascript-associative-arrays-considered-harmful/

However, you can use something like this:

function findPropertyWithValue(obj, val) {
    for (var i in obj) {
        if (obj.hasOwnProperty(i) && obj[i] === val) {
            return i;
        }
    }
    return null;
}

var arr = [];
arr['A string'] = '123';
arr['Another string'] = '456';
alert(findPropertyWithValue(arr, "123")); // 'A string'

Answer 3

inArray works for integer-access based arrays.

var len;

    if ( array ) {
        if ( indexOf ) {
            return indexOf.call( array, elem, i );
        }

        len = array.length;
        i = i ? i < 0 ? Math.max( 0, len + i ) : i : 0;

        for ( ; i < len; i++ ) {
            // Skip accessing in sparse arrays
            if ( i in array && array[ i ] === elem ) {
                return i;
            }
        }
    }

    return -1;

That's how jQuery does it. It does not iterate using a for(var i in arr)... (of course with the hasOwnProperty validation, it would be ;)) but only by index access according to length.

As the documentation says: http://api.jquery.com/jQuery.inArray/ it is similar to the native indexOf method. Seens the native indexOf does it this way, jQuery follows by having a similar behavior.