Typescript 2.5 adds JSDoc type assertion support for javascript file via ts-check service.
First of all, you should make sure you have typescript@2.5 install:
sudo npm i -g typescript@2.5
Then add @ts-check to the top of js file:
// @ts-check
This tell typescript to check the file.
Check type assertion we can do:
// index.js
function shouldBeNumber (/** @type {Number} */ num) {
'use strict';
console.log(num)
}
In VScode, if will use the function by passing the wrong param, we will get error in IDE.
shouldBeNumber("100");
But this doesn't stop the compiler, the code will still be compiled without error.
