How can I rectify the issue in TypeScript where the error "not all code paths return a value" occurs?

While developing an application, I encountered an error that says: "not all code paths return a value". The error is specifically in the function named addValues, indicating that the function must return "Obj[] | undefined".

Here is the code snippet in question:

public addValues() {

        const inputValue = document.getElementById('valor') as HTMLFormElement;

        const inputNameValue = 
        document.getElementById('nome-valor') as HTMLFormElement;

        const enterChecked = document.getElementById('entrada') as HTMLFormElement;
        const leftChecked = document.getElementById('saida') as HTMLFormElement;

        if (inputValue?.length && inputNameValue?.length && (enterChecked.checked || leftChecked.checked)) {
            const list: Obj = {
                id: Math.random(),
                valor: +inputValue,
                nomeValor: String(inputNameValue),
                checked: enterChecked.checked ? enterChecked : leftChecked
            }

            if (this.valores == undefined) {
                return undefined
            }

            return this.valores = [list]
        }

Answer №1

When you use your initial if statement, a decision point is created with two possible outcomes. If the condition is met and evaluates to true, the code block within is executed, containing two return statements. However, if the condition is false, the function reaches its end without returning any value. This is what is known as "not all code paths return a value".

It is important to define the return type of the function and ensure that a value of that type is returned in all possible branches.

Answer №2

The problem arises from having all return statements contained within the if block. It is crucial to include a return statement outside that block to ensure that the function does not return nothing in certain scenarios, thus maintaining the required return value of an object array or an undefined object, as specified.

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