A small refactor

a-small-refactor.js

// A quick refactor

// 1
function foo (fieldValue) {
    //If the fieldValue is a number, use ID
    //Otherwise, use codeName
    //Postgres gets grouchy about comparing strings to numbers
    let fieldName;
    try {
        const parsed = parseInt(fieldValue);
        if(isNaN(parsed)) {
            fieldName = 'codeName';
        } else {
            fieldName = 'id';
        }
    } catch(e) {
        //Nothing to worry about
        fieldName = 'codeName';
    }
}

// 2: separate type checking and behavior
function isNumber (value) {
    try {
        const parsed = parseInt(fieldValue);
        return !isNaN(parsed);
    } catch (error) {}
    return false;
}

function foo (fieldValue) {
    const fieldName = isNumber(fieldValue) ? 'id' : 'codeName';
}

// 3: parseInt() never throws
function foo (fieldValue) {
    const isNumber = !isNaN(parseInt(fieldValue));
    const fieldName = isNumber ? 'id' : 'codeName';
}

// 4: always provide a radix to parseInt()
function foo (fieldValue) {
    const isNumber = !isNaN(parseInt(fieldValue, 10));
    const fieldName = isNumber ? 'id' : 'codeName';
}

// 5? : use parseFloat so you don't have to worry about radix and an arrow function to make it a sweet one-liner
const foo = fieldValue => isNaN(parseFloat(fieldValue)) ? 'codeName' : 'id'