The variable 'x' is being referenced before being initialized

Question

The variable 'x' is being referenced before being initialized

Having trouble understanding the tsserver error in this static method from the Logger class.

LogLevel

const enum LogLevel {
    ERROR = 0,
    WARN = 1
}

export default LogLevel;

Logger

    static defaultHandler(level: LogLevel, ...message: readonly string[]) {
        if (!Logger.isLevelEnabled(level)) return;

        let handler: Function;
        switch (level) {
            case LogLevel.ERROR:
                handler = console.error;
                break;

            case LogLevel.WARN:
                handler = console.warn;
                break;
        }

        // [tsserver 2454] Variable 'handler' is used before being assigned
        handler(...message);
    }

Given that LogLevel is an Enum, the handler will never be unassigned. However, adding an if statement results in a complaint from tslint.

        // [tslint 1] expression is always true (strict-type-predicates)
        if (handler !== undefined) handler(...message);

The no-let rule was even removed from tslint because it does not recognize the assignment within the switch case and suggests using const handler: Function;. Can someone shed some light on this issue?

typescript

Answer 1

Answer №1

It appears that you are currently only handling errors and warnings in your code:

let handler: Function;
switch (level) {
    case LogLevel.ERROR:
        handler = console.error;
        break;

    case LogLevel.WARN:
        handler = console.warn;
        break;
}

However, there are more options available such as INFO, DEBUG, and VERBOSE:

ERROR = 0,
WARN = 1,
INFO = 2,
DEBUG = 3,
VERBOSE = 4

Solution

To address this issue, you should add a default case to handle the remaining log levels:

let handler: Function;
switch (level) {
    case LogLevel.ERROR:
        handler = console.error;
        break;

    case LogLevel.WARN:
        handler = console.warn;
        break;

    default: 
        handler = console.log;
        break;
}

Answer 2

It appears that you are currently only handling errors and warnings in your code:

let handler: Function;
switch (level) {
    case LogLevel.ERROR:
        handler = console.error;
        break;

    case LogLevel.WARN:
        handler = console.warn;
        break;
}

However, there are more options available such as INFO, DEBUG, and VERBOSE:

ERROR = 0,
WARN = 1,
INFO = 2,
DEBUG = 3,
VERBOSE = 4

Solution

To address this issue, you should add a default case to handle the remaining log levels:

let handler: Function;
switch (level) {
    case LogLevel.ERROR:
        handler = console.error;
        break;

    case LogLevel.WARN:
        handler = console.warn;
        break;

    default: 
        handler = console.log;
        break;
}

The variable 'x' is being referenced before being initialized

LogLevel

Logger

Answer №1

Solution

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