Javascript: Getting undefined on input box that takes a range from 0 to 10 -

i have 2 buttons (+ , -) , input box value of 10. input must take value 0 10 , can't figure out why i'm getting undefined after reach either 0 or 10 on input box. tried using parseint values. perhaps i'm not doing on right place. appreciate help.

var fighterscore1 = document.getelementbyid("fighterscore1");  fighterscore1.value  = 10;  var fighter1inc = document.getelementbyid("fighter1inc");  var valor = 10;    	fighter1inc.onclick = function (valor) {  		fighterscore1.value = increasevalue(valor);  	};  	fighter1dec.onclick = function (valor) {  		fighterscore1.value = decreasevalue(valor.value);  	};    function decreasevalue() {  		if (valor <= 0 ) {    	    } else {  	    valor--;  	    	return valor;  	    }  	};  	function increasevalue() {  		if (valor >= 10 ) {  	    	valor = 10;  	    } else {  	    valor++;  	    	valor = valor;  	    	return valor;  	    }  	      	};

<div id="rwid1">  			<button id="fighter1inc">+</button>  			<input type="text" id="fighterscore1" maxlength="10" onkeypress='return event.charcode >= 48 && event.charcode <= 57'>  			<button id="fighter1dec">-</button>  		</div><!--/rwid-->

the problem you're returning inside condition less 10 or greater 0. if don't return in 1 condition,there no return value end assigning undefined variable. here fixed jsfiddle. have return outside if statements, , valor.value doesn't exist.

var fighterscore1 = document.getelementbyid("fighterscore1");  fighterscore1.value  = 10;  var fighter1inc = document.getelementbyid("fighter1inc");  var valor = 10;    fighter1inc.onclick = function (valor) {  	fighterscore1.value = increasevalue();  };    fighter1dec.onclick = function (valor) {  	fighterscore1.value = decreasevalue();  };    function decreasevalue() {  	if (valor <= 0 ) {          valor = 0;  	} else {  	    valor--;  	}  	return valor;  };    function increasevalue() {  	if (valor >= 10 ) {  	    valor = 10;  	} else {  	    valor++;  	}      return valor;  };

<div id="rwid1">  	<button id="fighter1inc">+</button>  	<input type="text" id="fighterscore1" maxlength="10" onkeypress='return event.charcode >= 48 && event.charcode <= 57'>  	<button id="fighter1dec">-</button>  </div><!--/rwid-->

a note: pass arguments function takes none (js accepts varying number of arguments, if don't specify). either remove call arguments, or use argument , pass in, using argument in place of valor.