How to use basic programming skill to improve your code

note.md

Please good use of programming basic skills

Do you know what recursive, IIFE, ternary operation, and short circuit are? A basic-level developer/programmer should know these skills which can make you code simplify so much.

First, let's look this code:

checkError(obj) {
    let errorMessage = ''
    if (!_.isNull(obj)) {
        if (!_.isUndefined(obj.error)) {
            if (!_.isUndefined(obj.error.error)) {
                errorMessage = obj.error.error
            } else {
                errorMessage = obj.error
            }
        } else {
            errorMessage = obj
        }
        if (errorMessage !== '') {
            if (!_.isUndefined(errorMessage.message)) {
                SimpleAlert.alert('Error', errorMessage.message)
            } else {
                SimpleAlert.alert('Error', errorMessage)
            }
        }
    }// isNull
}

Could you directly understand this code how to work? Let's split two sections.

First section:

if (!_.isUndefined(obj.error)) {
    if (!_.isUndefined(obj.error.error)) {
        errorMessage = obj.error.error
    } else {
        errorMessage = obj.error
    }
} else {
    errorMessage = obj
}

Second section:

if (errorMessage !== '') {
    if (!_.isUndefined(errorMessage.message)) {
        SimpleAlert.alert('Error', errorMessage.message)
    } else {
        SimpleAlert.alert('Error', errorMessage)
    }
}

First section is to find error object. It needs to pass two-nested if-else until it gets error object.

Second section is to get message property from the error object

// The code has 16 lines
let checkErrorV1 = (obj: any) => {
    // Validate: Finish function life cycle if obj is null
    if (obj === null) return;

    // get errorMessage
    let errorMessage = (function getErrorMessage(obj: any) {
        let isUndefined = obj.error === undefined;
        return isUndefined ? obj : getErrorMessage(obj.error);
    })(obj);
    if (!errorMessage) return;

    // submit errorMessage by SimpleAlert   
    let isUndefined = errorMessage.message === undefined;
    let message = isUndefined ? errorMessage: errorMessage.message;
    SimpleAlert.alert('Error', message)
}

// The code has 15 lines
let checkErrorV2 = (obj: any) => {
    // Validate: Finish function life cycle if obj is null
    if (obj === null) return;

    // get errorMessage
    let errorMessage = (function getErrorMessage(obj: any) {
        let isUndefined = obj.error === undefined;
        return isUndefined ? obj : getErrorMessage(obj.error);
    })(obj);
    if (!errorMessage) return;

    // submit errorMessage by SimpleAlert   
    let message = errorMessage.message || errorMessage;
    SimpleAlert.alert('Error', message)
}

// The code has 13 lines
let checkErrorV3 = (obj: any) => {
    if (!obj) return;  // isNull or isUndefined

    // get errorMessage
    let error = (function getError(obj: any) {
        return obj.error ? getError(obj.error) : obj;
    })(obj);
    if (!error) return;  // isNull or isUndefined

    // submit errorMessage by SimpleAlert
    let message = error.message || error;
    SimpleAlert.alert('Error', message)
}


// The code has 12 lines
let checkErrorV3 = (obj: any) => {
    if (!obj) return;  // isNull or isUndefined

    // get errorMessage
    let getError = obj => obj.error ? getError(obj.error) : obj;
    let error = getError(obj);
    if (!error) return;  // isNull or isUndefined

    // submit errorMessage by SimpleAlert
    let message = error.message || error;
    SimpleAlert.alert('Error', message)
}