How do I use a default parameter in JavaScript?

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Default Parameter

Syntax: –
function function_name (para1, para2=“value”, para3) // problem undefined
{
Block of statement;
}
Syntax: –
function function_name (para1, para2=“value1”, para3=“value2”)
{
Block of statement;
}

JavaScript also allows the use of arrays and null as default values.

Rest Parameters

The rest parameter allows representing an indefinite number of arguments as an array.

Syntax: –
function function_name (…args)
{
Block of statement;
}

Syntax: –
function function_name (a, …args)
{
Block of statement;
}

The rest operator must be the last parameter to a function.

Rest Vs Arguments

There are three main differences between the rest parameters and the arguments object:-

Rest parameters are only the ones that haven’t been given a separate name, while the arguments object contains all arguments passed to the function.
The arguments object is not a real array, while Rest Parameters are Array instances, meaning methods like sort, map, forEach or pop can be applied on it directly.
The arguments object has additional functionality specific to itself (like the callee property).

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