CODEWITHSUNDEEP
javascript
Vishal Suri
Vishal Suri

Reputation: 455

How can a javascript function, called with single argument, can call function with varying arguments?

I am working on a php application, in which I have the following existing code:

<ul>
   <li><a href="#" id="BillingP" onClick="change_main_Selection(this);">Paper</a></li>
   <li><a href="#" id="BillingE" onClick="change_main_Selection(this);">Electronic</a></li>
   <li><a href="#" id="BillingE" onClick="change_main_Selection(this,'CLHReports');">Clearing House Reports</a></li>
   <li><a href="#" id="BillingCP" onClick="change_main_Selection(this);">Capitation</a></li>
</ul>

As you can see function change_main_Selection(this) gets called, when user clicks on tab. I have tried to find change_main_Selection() definition and found following:

function change_main_Selection(main_tab, sub_tab, redirect_url, flgNc, onload){
    var main_tab_obj = main_tab;
    var sub_tab_obj = sub_tab;
}

My confusion is that while calling change_main_Selection(), it only takes single argument. But how can it call change_main_Selection() function with multiple arguments.

Upvotes: 0

Views: 94

Answers (3)

Pankaj Shukla
Pankaj Shukla

Reputation: 2672

Javascript functions are called variadic functions. You can pass less params or more params. When you pass less params, extra params are set to undefined. If you pass more, you can see them in a special array like object called arguments.

See below example when you pass more arguments.

function sum() {
var s = 0;  
for(var i=0;i<arguments.length;i++){
        s+= arguments[i];
}
return s;
}

var ans = sum(1,2,3);
console.log(ans);//6

Upvotes: 1

KAD
KAD

Reputation: 11122

A JavaScript function does not perform any checking on parameter values (arguments).

If a function is called with missing arguments (less than declared), the missing values are set to: undefined

Sometimes this is acceptable, but sometimes it is better to assign a default value to the parameter:

function myFunction(x, y) {
    y = y || 'defaultValue'; // overwrites falsey values (0, null, false)

    // better approach
    if (typeof y === 'undefined') { y = 'defaultValue'; }
}

With ES6, you can provide default values in a C++ style default values as follows:

function myFunction(x, y='defaultValue'){}

Upvotes: 2

Yashar Aliabbasi
Yashar Aliabbasi

Reputation: 2739

You can access to arguments by arguments variable inside your function as explained in w3schools this means there is no need to declare any parameter explicitly in your function:

x = findMax(1, 123, 500, 115, 44, 88);
console.info(x);
function findMax() {
  var i;
  var max = -Infinity;
  for (i = 0; i < arguments.length; i++) {
    if (arguments[i] > max) {
      max = arguments[i];
    }
  }
  return max;
}

and you can access them by arguments variable

Upvotes: 0

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