A chainable function is one where we are able to do this:
// These functions are chained
someFunction()
.getSomething()
.setSomething()
.saveSomething();
// These function are not chained
let result = someFunction();
result.getSomething();
result.setSomething();
result.saveSomething();
A very subtle difference in that chainable functions "hide" the object they are working with.
Typescript Intellisense
For a refresher on what Typescript is really about:
Typescript's intellisense uses its own language service to power autocompletion. Without diving too deep, if we as programmers adjust our thing to doing everything the Typescript way, we get, for free, classes and function which always work with Intellisense.
If we adopt the methods shown below we get the free Chainable option too.
Todo: Give examples
JWP2020 Chainable Functions in Typescript