Theo's Typesafe Cult•3y ago

Is this intended JS behavior?

Came across this problem when using switch statements. Doesnt seem like each case has its own scope, however, you cannot access a variable outside of the case it was defined in (which i wasnt expecting to be able to do anyway, but if i did it would at least make sense) despite not being able to share variable names from case to case. Take the following example

function test() {
    const test = "testvar";
    
    switch (test) {
        case "testvar":
            const otherTest = "result";    
        break;
        
        case "test":
            const otherTest = "resultTwo"; // SyntaxError: Identifier 'otherTest' has already been declared
        break;
    }
}

function test() {
    const test = "testvar";
    
    switch (test) {
        case "testvar":
            const otherTest = "result";    
        break;
        
        case "test":
            const otherTest = "resultTwo"; // SyntaxError: Identifier 'otherTest' has already been declared
        break;
    }
}

This also errors out

function test() {
    const test = "testvar";
    
    switch (test) {
        case "testvar":
            const otherTest = "result";    
        break;
        
        case "test":
            const otherTestNew = "resultTwo";
        break;
    }

    console.log(otherTest); // ReferenceError: otherTest is not defined
}

function test() {
    const test = "testvar";
    
    switch (test) {
        case "testvar":
            const otherTest = "result";    
        break;
        
        case "test":
            const otherTestNew = "resultTwo";
        break;
    }

    console.log(otherTest); // ReferenceError: otherTest is not defined
}

I understand that a let variable can just be made outside of the switch statement and then be mutated across each case but i just found this behavior very interesting

4 Replies

John•3y ago

I’d use objects instead of switch tho

Unknown User•3y ago

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iMagicOP•3y ago

Yup. If we're following regular JS scoping rules it makes sense to me why i would get a reference error there. That second example was just delving deeper into this

(which i wasnt expecting to be able to do anyway, but if i did it would at least make sense)

I guess what my post boils down to ultimately is why i wouldnt be able to define variables under the same name across different cases

Unknown User•3y ago

Message Not Public

Gaming

Programming

Is this intended JS behavior?