Javascript : Assign a function and pass parameter at the same time
Question
I have html buttons "classA","classB" and "classC" to which I assign the onclick handler function as follows..
var classA = document.getElementById('classA');
classA.onclick = filterByClassA;
var classB = document.getElementById('classB');
classB.onclick = filterByClassB;
var classC = document.getElementById('classC');
classC.onclick = filterByClassC;
These 3 functions do the same thing, only difference being the class. So, can I have a single function assigned to these buttons, called with different parameters for each button. Something like below
var classA = document.getElementById('classA');
classA.onclick = filterByClass('classA');
var classB = document.getElementById('classB');
classB.onclick = filterByClass('classB');
var classC = document.getElementById('classC');
classC.onclick = filterByClass('classC');
I know this is a function call and not assignment and this is wrong but is there a way I can achieve this ie assign a function and pass parameter at the same time but not call it?
3 answers
solution1
6 ACCPTED 2013-06-07 08:46:18
function filterByClass(className)
{
return function()
{
// Do something with className
console.log(className);
}
}
solution2
3
Bind can help you out here: Its called partial application.
Bind Syntax
fun.bind(thisArg[, arg1[, arg2[, ...]]])
- 1st param is scope of the function when it is called.
- From 2nd you can pass any number of agruments. See the below code to know how it works.
Code:
var classA = document.getElementById('classA');
classA.onclick = filterByClass.bind(classA, 'classA');
var classB = document.getElementById('classB');
classB.onclick = filterByClass.bind(classB, 'classB');
var classC = document.getElementById('classC');
classC.onclick = filterByClass.bind(classC, 'classC');
function filterByClass(className, eventObject) {
console.log(this, className, eventObject);
}
Update:
Check out the Compatibility section in the above MDN link. You may need to use it, if you are going to use bind in non modern browsers.
solution3
1 2013-06-07 08:57:27
i always try to keep the code as short as possible
so if your buttons are inside a container you can do that.
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>atest</title>
<script>
window.onload=function(){
var c=document.getElementsByTagName('div')[0].childNodes,
l=c.length,
filterByClass=function(){
console.log(this.id);//this.id is the classA or whatever
};
while(l--){
c[l].onclick=filterByClass;
}
}
</script>
</head>
<body>
<div>
<button id="classA">A</button>
<button id="classB">B</button>
<button id="classC">C</button>
</div>
</body>
</html>
in this case
document.getElementsByTagName('div')[0]
returns the first div in the document
childNodes
give u the list of the buttons inside that div
the while function adds the onclick event with your function 'filterByClass'
inside filterByClass u can access the element by this and so return it's id with this.id
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