Typescript Type Annotations throws 'Unexpected token ":"'

I am trying to annotate my variables with types but when running the code it simply gives off an error:

let foo: number = 23;
console.log( foo );

// let foo: number = 23;
          ^

// SyntaxError: Unexpected token ':'
// [90m    at Object.compileFunction (node:vm:352:18)[39m
// [90m    at wrapSafe (node:internal/modules/cjs/loader:1031:15)[39m
// [90m    at Module._compile (node:internal/modules/cjs/loader:1065:27)[39m
// [90m    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1153:10)[39m
// [90m    at Module.load (node:internal/modules/cjs/loader:981:32)[39m
// [90m    at Function.Module._load (node:internal/modules/cjs/loader:822:12)[39m
// [90m    at Function.executeUserEntryPoint [as runMain] // (node:internal/modules/run_main:79:12)[39m
// [90m    at node:internal/main/run_main_module:17:47[39m

>Solution :

You have two options:

First compile it to plain JS with tsc myfile.ts and run the JS file with node myfile.js.

Or npm install ts-node which lets you run TS files like you would run JS files: ts-node myfile.ts