javascript if statement multiple operators failing

Question

I have an if statement which evaluates

if(expression || expression &&
   expression || expression){

   //logic
}

for a reason I cannot understand, the else statement after the and operator does not get evaluated. Is there some rules to the if statement that I do not know of?

Here is my code:

const fillTable = function (array) {
    let tbody = document.querySelector("#tblbody");
    while (tbody.firstChild) {
        tbody.removeChild(tbody.firstChild);
    }
    array.forEach(element => {
        let region = regionOption.options[regionOption.selectedIndex].value;
        let gender = genderOption.options[regionOption.selectedIndex].value;
        elementGender = Object.values(element)[2];
        elementRegion = Object.values(element)[3];
        console.log(elementRegion + "+" + region);
        console.log(elementGender + "+" + gender);

        if (elementRegion === region || region === "All" &&
            elementGender === gender || gender === "bot") {
            let tr = document.createElement("tr");
            tbody.appendChild(tr);
            const values = Object.values(element);
            values.forEach(element => {
                let td = document.createElement("td");
                td.appendChild(document.createTextNode(element));
                tr.appendChild(td);
            })
        }
    })
};

the loop continues even though the genders does not match in the if statement.

Order of operations... A good linter built into your IDE would be yelling at you for this. :) — epascarello
– epascarello, Commented Jan 11, 2019 at 21:53
@epascarello I am using Visual Studio Code for this. No warnings :) — Jonas Grønbek
– Jonas Grønbek, Commented Jan 11, 2019 at 23:24

David · Accepted Answer · 2019-01-11 21:21:43Z

1

You're probably getting tripped up on operator precedence. If the boolean expressions before and after the && are supposed to be grouped, explicitly group them:

if((expression || expression) &&
   (expression || expression))

Even in the absence of operator precedence rules, it's always best to be clear and explicit about the logic you're expressing.

answered Jan 11, 2019 at 21:21

David

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1 Comment

Jonas Grønbek Over a year ago

Thanks for the fast answer, I will mark you as soon as I am able to

JJWesterkamp · Accepted Answer · 2019-01-11 21:23:28Z

1

It looks like the 2 lines from the if condition should each be within their own grouping operator:

if (
       (expression1 || expression2)
    && (expression3 || expression4)
) {
    // ...
}

answered Jan 11, 2019 at 21:23

JJWesterkamp

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Comments

Mitul · Accepted Answer · 2019-01-11 21:23:31Z

1

I guess you intended this

if ((elementRegion === region || region === "All") && 
     (elementGender === gender || gender === "bot"))

All the logical operators are chaining without parenthesis.

answered Jan 11, 2019 at 21:23

Mitul

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