Hy i dont know if that is possible but i want to set a given variable in js per reference.
What i want to do is, that each time i pass a string to the function addstring that the value of the textfield is added like +=
function addstring(string)
{
document.getElementById("string").value = string; // its a textfield
}
How can i do that?
document.getElementById("string").value = document.getElementById("string").value + string;
+= works fine.
var str = "stack";
str += "overflow";
console.log(str); //alert(str); Use firebug!!
stackoverflow
When passing in a primitive type variable like a string or a number, the value is passed in by value. This means that any changes to that variable while in the function are completely separate from anything that happens outside the function. Let’s take a look at the following example:
function myfunction(x)
{
// x is equal to 4
x = 5;
// x is now equal to 5
}
var x = 4;
alert(x); // x is equal to 4
myfunction(x);
alert(x); // x is still equal to 4
Passing in an object, however, passes it in by reference. In this case, any property of that object is accessible within the function. Let’s take a look at another example:
function myobject()
{
this.value = 5;
}
var o = new myobject();
alert(o.value); // o.value = 5
function objectchanger(fnc)
{
fnc.value = 6;
}
objectchanger(o);
alert(o.value); // o.value is now equal to 6
Javascript does not support passing parameters by reference.
This link offers a good breakdown and some workarounds- Passing by Value or reference
Your code example will work just fine with +=; complete example below. This suggests the problem you're having lies elsewhere.
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-type" content="text/html;charset=UTF-8">
<title>Test Page</title>
<style type='text/css'>
body {
font-family: sans-serif;
}
</style>
<script type='text/javascript'>
function addstring(string)
{
document.getElementById('string').value += string;
}
</script>
</head>
<body><div>
<input type='text' id='string' value=''>
<br><input type='button' value='One' onClick="addstring('one');">
<input type='button' value='Two' onClick="addstring('two');">
<input type='button' value='Three' onClick="addstring('three');">
</div></body>
</html>