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JavaScript

function joinObjects( array ) {
	
    // Start with empty array
    var ret = new Array();
    
    // Iterate array
    for ( var i = 0; i < array.length; i++ ) {
    
        // Search by fieldname
        var match = false;
        var j;
        for ( j = 0; j < ret.length; j++ ) {
        	if ( array[i].Fieldname == ret[j].Fieldname ) { match = true; break; }
        }
        
        // If not exists
        if ( !match ) {
        	
            // Intert object
            ret.push({
            	Fieldname: array[i].Fieldname,
                Value: new Array()
            });
            
        }
        
        // Insert value
        ret[j].Value.push( array[i].Value );
        
    }
    
    // Return new array
    return ret;
    
}

var arr = [
 {Fieldname: 'Übergeordnete TEC_Equipment', Value: 'E0192'}, 
 {Fieldname: 'Übergeordnete TEC_MapLocation', Value: 'M100'}, 
 {Fieldname: 'Übergeordnete TEC_MapLocation', Value: 'M200'},
 {Fieldname: 'Übergeordnete TEC_FunctionalLocation', Value: 'FL456'}
];

joinObjects(arr);