At compile time, Typescript runs smoothly, but errors may arise during runtime

Currently, I am delving into learning Typescript and have encountered a snag in my code. Despite searching extensively for a solution, I have been unable to find any relevant material pertaining to my issue. Below is the code snippet in question:

<code>
class Hello{
    lars: string;

    constructor(name: string) {
        this.lars = name;
    }

    sayHello(){
        return `hello ${this.lars}`;
    }
}

let b = new Hello('Metallica');
</code>

Upon compiling the code using 'tsc test.ts', it compiles without any errors. However, upon running it with 'node test.ts', an error is thrown:

<blockquote>

lars: string;
        ^

SyntaxError: Unexpected token :
    at createScript (vm.js:80:10)
    at Object.runInThisContext (vm.js:139:10)
    at Module._compile (module.js:616:28)
    at Object.Module._extensions..js (module.js:663:10)
    at Module.load (module.js:565:32)
    at tryModuleLoad (module.js:505:12)
    at Function.Module._load (module.js:497:3)
    at Function.Module.runMain (module.js:693:10)
    at startup (bootstrap_node.js:188:16)
    at bootstrap_node.js:609:3
</blockquote>

The file runs when using 'Node test.js', but unfortunately does not yield the expected output of "Hello Metallica", while 'node test.ts' fails.

Here is the compiled code for reference:

var Hello = /** @class */ (function () {
    function Hello(name) {
        this.lars = name;
    }
    Hello.prototype.sayHello = function () {
        return "hello " + this.lars;
    };
    return Hello;
}());
var b = new Hello('Metallica');

Answer №1

The typescript itself is not the issue here. The reason you are not getting the desired outcome is because:

  1. You are attempting to execute the typescript directly. Remember, typescript needs to be compiled into javascript before it can be run. You can do this by using a tool like node. Try running node test.js
  2. There is no code in your file that outputs to the console. Consider modifying the last line to something like
    console.log(new Greeting('World').sayHello());
    .

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