Some concepts to consider when writing code

STRY0048487_peer_review.js

// Original & refactored with comments noting changes & reasoning

// Original
function validateSearchRequest(parent_space_id, event_start, event_end) {

    var isValid = true;
    var message = '';

    if (!this.moment(event_start).isValid()) {
        isValid = false;
        message = 'Invalid start datetime.';
    }
    else if (!this.moment(event_end).isValid()) {
        isValid = false;
        message = 'Invalid end datetime.';
    }
    else if (this.moment(event_start).isAfter(this.moment(event_end))) {
        isValid = false;
        message = 'The end date must not be before the start date.';
    }

    var result = {
        'isValid': isValid,
        'message': message
    };

    return result;

},

// Refactored
function validateSearchRequest(parent_space_id, event_start, event_end) {

    // Consider constructing the entire return payload at the start so next dev
    // can reason about the shape of the return from the start
    var returnResult = {
        isValid: false,     // Consider starting off with a default object that is invalid, validate at the end
        message: ""
    };

    // Move logic for validation into individual variables, keep boolean logic in if
    // blocks simpler for readability
    var valid_start = this.moment(event_start).isValid();
    if (!valid_start) {
        // Since result is false to begin with, we just need to add a message
        returnResult.message = 'Invalid start datetime.';
        // Returning if validation fails means rest of function won't even be considered
        // Returning early also helps the next dev reading the code more easily reason
        // about the logical flow. If else's tend to open new paths of code execution
        // which can be difficult to reason about for the next dev (which might be yourself 
        // in the future). In this simple case, it seems trivial but as the logic becomes more 
        // complex, following this pattern will immensly improve code readability
        return returnResult;
    }

    var valid_end = this.moment(event_end).isValid()
    if (!valid_end) {
        returnResult.message = 'Invalid end datetime.';
        return returnResult;
    }

    var end_is_after_start = this.moment(event_end).isAfter(this.moment(event_start));
    if (!end_is_after_start) {
        returnResult.message = 'The end date must not be before the start date.';
        return returnResult;
    }

    // If we make it past all the guard blocks -- we can validate the response and return
    // successfully
    returnResult.isValid = true;

    return returnResult;

}