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Javascript Parameters and arguments

In JavaScript, parameters and arguments refer to values passed into functions, but they serve different roles in function definition and invocation.

Parameters

Parameters are variables listed as part of a function’s definition.
They act as placeholders that allow a function to accept input when it is called.

1function greet(name, age) { 
2    console.log(`Hello ${name}, you are ${age} years old.`);
3}
4

In this example, name and age are parameters of the greet function.

Arguments

Arguments are the actual values passed to the function when it is called (invoked).
They are the data that gets passed to the function parameters.

1greet("Amir", 30);

Here, "Amir" and 30 are arguments passed to the greet function. They correspond to the parameters name and age.

Key Points

Number of Parameters and Arguments: JavaScript functions don’t enforce matching numbers of parameters and arguments. Extra arguments are ignored, while missing ones default to undefined.
Default Parameters: JavaScript allows setting default parameter values if no argument is provided for a parameter.

1function greet(name = "Guest") {
2    console.log(`Hello ${name}`);
3}
4greet(); // Outputs: "Hello Guest"
5

Defining functions in Javascript (function keyword, arrow functions)

Functions Return values