ts-morph

Parameters

Parameters can be retreived from nodes by calling getParameters():

const parameters = functionDeclaration.getParameters();

Inserting/Adding

Insert or add parameters by calling insertParameter(), insertParameters(), addParameter(), or addParameters().

For example:

const parameter = functionDeclaration.insertParameter(1, {
    name: "param1",
    type: "string"
});

Removing

Remove a parameter by calling .remove() on it:

parameter.remove();

Rest parameter

Tell if a parameter is a rest parameter:

const isRestParameter = parameter.isRestParameter(); // returns: boolean

Or set a parameter as a rest parameter:

parameter.setIsRestParameter(true);

Parameter Property

Constructor parameters may be properties when they have a scope and/or are readonly. You can tell if one is by calling:

const isParameterProperty = parameter.isParameterProperty(); // returns: boolean

Optional

A parameter can be optional if it is marked so with a question mark, is a rest parameter, or has an initializer.

isOptional() can be used to tell if any of these are true:

const isOptional = parameter.isOptional(); // returns: boolean