In JavaScript, EVERY parameter is considered optional. If no value is supplied, then it is treated as undefined. So while writing functions in TypeScript, we can make a parameter optional using the “?” after the parameter name.

function Demo(arg1: number, arg2? :number) {
}

So, arg1 is always required and arg2 is an optional parameter. Remember, optional parameters must FOLLOW required parameters. If we want to make arg1 optional, instead of arg2, then we need to change the order and arg1 must be put after arg2.

function Demo(arg2: number, arg1? :number) {
}

Similar to optional parameters, default parameters are also supported.

function Demo(arg1: number, arg2 = 4) {
}

In JavaScript, every parameter is considered optional. If no value is supplied, then it is treated as undefined. So while writing functions in TypeScript, we can make a parameter optional using the “?” after the parameter name.

function Demo(arg1: number, arg2? :number) {
}

So, arg1 is always required and arg2 is an optional parameter. Remember, optional parameters must follow required parameters. If we want to make arg1 optional, instead of arg2, then we need to change the order and arg1 must be put after arg2.

function Demo(arg2: number, arg1? :number) {
}

Similar to optional parameters, default parameters are also supported.

function Demo(arg1: number, arg2 = 4) {
}