CODEWITHSUNDEEP
javascriptparameters
user4221591
user4221591

Reputation: 2180

different types of parameters in javascript function

I am quite new to javascript. When going through the javascript codes, I have found ::

function Method1(sender, args) { ... }
function Method2(source, arguments) { ... }

When to use (sender, args) and (source, arguments)? What do they mean?

Upvotes: 0

Views: 203

Answers (1)

ghybs
ghybs

Reputation: 53370

arguments is actually not a JS reserved word, otherwise your Method2 would not have worked and would have thrown a Syntax Error.

When arguments is used in the parameters list of a function, it is simply a regular function parameter / argument, exactly like your sender, source and args.

It is true now that Arguments cannot be used as a class name. It is used internally by JavaScript to create an arguments object (that is the one referred to by Tushar in the comments).

When control enters an execution context for function code, an arguments object is created unless (as specified in 10.5) the identifier arguments occurs as an Identifier in the function’s FormalParameterList or occurs as the Identifier of a VariableDeclaration or FunctionDeclaration contained in the function code.

In every function, you can access all the parameters passed during that function call using this arguments array-like object. It is very useful for functions that may accept a non-predetermined (and possibly unlimited) number of parameters.

So what happens with your Method2 is that it uses the same identifier "arguments" which now is assigned just a single parameter. As if it had shadowed the built-in arguments object.

Whereas if it had not been used in the parameters list, arguments within the function block would have been automatically assigned the list of all parameters.

Demo: http://jsfiddle.net/5cexbrff/ (see result in the console)

Upvotes: 1

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