I am very new to node.js and typescript. I am trying to learn by porting an existing application over from python. I am getting a syntax error in a place I do not expect.

I have a class that is the workhorse of the project. It is in a file called myClass.ts

myProject
└── js
    ├── commands
    │   └── rules.js
    ├── myClass.ts
    └── main.js

rules.js includes myClass as:

try {
    const {myClass} = require("../myClass.ts")
} catch(e) {
    console.log(e)
}

I am using PyCharm and can put a breakpoint in the catch block. The error points to the constructor in the class. The error is:

/home/me/PycharmProjects/myProject/js/myClass.ts:44
        rule_type: string,
                ^

SyntaxError: Unexpected token ':'
    at Object.compileFunction (node:vm:352:18)
    at wrapSafe (node:internal/modules/cjs/loader:1031:15)
    at Module._compile (node:internal/modules/cjs/loader:1065:27)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1153:10)
    at Module.load (node:internal/modules/cjs/loader:981:32)
    at Function.Module._load (node:internal/modules/cjs/loader:822:12)
    at Module.require (node:internal/modules/cjs/loader:1005:19)
    at require (node:internal/modules/cjs/helpers:102:18)
    at Object.<anonymous> (/home/me/PycharmProjects/myProject/js/commands/rules.js:4:19)
    at Module._compile (node:internal/modules/cjs/loader:1101:14)

myClass is too big to fit in here. It starts:

const {randomInt} = require('crypto')

class myClass {
    constructor(
        rule_type: string,
        display_type: string,
        range_min: number     = 1,
        range_max: number     = 10000,
        display_mapping: {}   = undefined,
        value_adjustments: {} = undefined,
    ) {
        this.rule_type = die_type
        this.display_type = display_type
        this.range_min = Math.trunc(range_min)
        this.range_max = Math.trunc(range_max)
        this.display_mapping = display_mapping
        this.value_adjustments = value_adjustments
    }

    ...//a bunch of methods, etc
}

exports.myClass = myClass;

If I take the : string type hint away, then the error just falls down to the next type hint. Is there a problem mixing javascript and typescript in this way?

Why am I mixing js and ts? I found a sample node project that seems to be a reasonable starting point for what I want to do. I figured that trying out typescript for this class might be a good exercise.

** Edit **

Thanks to all. Much to learn...