How to have optional parameters with default values

[wyo]

I have a function with several parameter, each optional.

function test (a, b, c, d) {...}

How do I check if e.g. parameter "a" is missing and set it a default
value?
How can I use it with parameter "a" optional but "b", "c", "d"
specified?

O. Wyss

 

[scripts.contact]

I have a function with several parameter, each optional.

function test (a, b, c, d) {...}

How do I check if e.g. parameter "a" is missing and set it a default
value?

if(a===undefined)a='default value'

How can I use it with parameter "a" optional but "b", "c", "d"
specified?

if(b===undefined)doSomething()

 

[wyo]

if(b===undefined)doSomething()

and calling it as

test (,value_b, value_c, value_d);

Just leave off parameter "a"?

O. Wyss

 

[RobG]

I have a function with several parameter, each optional.

function test (a, b, c, d) {...}

How do I check if e.g. parameter "a" is missing and set it a default
value?

The first parameter passed to the function will be assigned to a, the
second to b, etc. If a is missing, then so are b, c and d.

function test (a, b, c, d, a) {
a = a || 'a';
b = b || 'b';
...
}

How can I use it with parameter "a" optional but "b", "c", "d"
specified?

function test (b, c, d, a) {...}

Parameters are passed by order, not name.

 

[wyo]

Parameters are passed by order, not name.

That means I've to give a dummy value like -1 for the first
parameter.

Thanks
O. Wyss

 

[scripts.contact]

That means I've to give a dummy value like -1 for the first
parameter.

yes e.g. 0, empty string, null, undefined etc..