What is the rationale behind TypeScript's decision to permit omission of "this" in a method?

Question

What is the rationale behind TypeScript's decision to permit omission of "this" in a method?

The TypeScript code below compiles without errors:

class Something {

    name: string;

    constructor() {
        name = "test";
    }

}

Although this code compiles successfully, it mistakenly assumes that the `name` variable exists. However, when compiled to JavaScript, it will throw an error because I overlooked using the this keyword:

/Users/cburtbrown/Documents/code/ts/js/tstest.js:6
        console.log(name);
                    ^

ReferenceError: name is not defined
    at Something.action (/Users/cburtbrown/Documents/code/ts/js/tstest.js:6:21)
    at Object.<anonymous> (/Users/cburtbrown/Documents/code/ts/js/tstest.js:10:25)
    at Module._compile (module.js:541:32)
    at Object.Module._extensions..js (module.js:550:10)
    at Module.load (module.js:456:32)
    at tryModuleLoad (module.js:415:12)
    at Function.Module._load (module.js:407:3)
    at Function.Module.runMain (module.js:575:10)
    at startup (node.js:159:18)
    at node.js:444:3

If I make a typo in the variable within the constructor, I receive the following error:

Cannot find name 'namej'

Shouldn't this error be triggered even if the variable is spelled correctly?

javascript typescript

Answer 1

Answer №1

Due to the existence of a name property in the window object, this operation is being attempted.

However, TypeScript does not support assigning values to this property, resulting in failure when executed outside the browser environment.

To confirm this, try assigning a value to any other properties of the window object.

For instance:

class Something {
    name: string;

    constructor() {
        status = "test";
    }
}

Answer 2

Due to the existence of a name property in the window object, this operation is being attempted.

However, TypeScript does not support assigning values to this property, resulting in failure when executed outside the browser environment.

To confirm this, try assigning a value to any other properties of the window object.

For instance:

class Something {
    name: string;

    constructor() {
        status = "test";
    }
}

What is the rationale behind TypeScript's decision to permit omission of "this" in a method?

Answer №1

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