Javascript - checking if multiple fields are empty not working

Question

HTML form look:

<form action="search" id="searchForm" onsubmit="return validateSearch()">
    <input type="text" name="byTitle" pattern="[a-zA-Z0-9]+" placeholder="Enter a word from title">
    <input type="text" name="byAuthor" pattern="[a-zA-Z]+\s[a-zA-Z]+" placeholder="First-name Last-name"> <!--  pattern="\w+ \w+" -->
    <input id="startDate" name="startDate" type="date">
    <input id="endDate" name="endDate" type="date">
    <input type="submit" name="submit" value="Submit">
</form>

Javscript validating function:

function validateSearch() {

    var byTitle   = document.getElementById('searchForm').byTitle.value;
    // alert(byTitle);
    var byAuthor  = document.getElementById('searchForm').byAuthor.value;
    // alert(byAuthor);
    var startDate = document.getElementById('searchForm').startDate.value;
    //alert(startDate);
    var endDate   = document.getElementById('searchForm').endDate.value;
    //alert(endDate);       

    if(byTitle == byAuthor == startDate == endDate == ""){
        alert("Enter at least one search parameter!");
        return false;
    }
}

Now, if I leave all form fields empty/unfilled and press submit, alert("Enter at least one search parameter!"); message should pop-up, but it doesn't. Wanted to see what are the values of each field I have inserted alert after each field reading, and they are all same, empty string/blank. So, why is then that if condition not seeing them as same, empty fields?

Answer 1

Your issue is here:

wrong

if(byTitle == byAuthor == startDate == endDate == ""){

correct

if(byTitle === "" && byAuthor ==="" && startDate ==="" && endDate === ""){

Javascript has a simpler way to evaluate if a value is null, empty string or 0 by only evaluating the variable:

if(!byTitle  && !byAuthor && !startDate && !endDate ){ 

Another advise I wanted to share is to use "===" instead of "==".