CODEWITHSUNDEEP
javascriptif-statement
fullOfQuestions
fullOfQuestions

Reputation: 453

javascript "less than" if statement failing

Here is my function:

function reCalculate(i) {
    document.getElementById("Q" + i).value = document.getElementById("C" + i).value - document.getElementById("QA" + i).value;

    if (document.getElementById("Q" + i).value < 0) {
        document.getElementById("Q" + i).value = 0;
    }
    if (document.getElementById("Q" + i).value < document.getElementById("E" + i).value && document.getElementById("Q" + i).value != 0) {
        alert(document.getElementById("Q" + i).value + " is less than " + document.getElementById("E" + i).value + "?");
        document.getElementById("Q" + i).value = document.getElementById("E" + i).value;
    }
    document.getElementById("Q" + i).value = Math.ceil(document.getElementById("Q" + i).value);
}

It checks Q, if it's less than 0, it makes it 0. Then, if it's not 0, but it's less than E, it makes it E. For some reason this function works UNLESS Q is a double digit number.

For example, if Q is 7 and E is 2, then it will leave Q at 7. However, if Q is 10 and E is 2, for some reason it thinks that 10<2, and it changes Q to 2!

Am I missing something here??

Upvotes: 3

Views: 8497

Answers (4)

techfoobar
techfoobar

Reputation: 66663

Thats because it is considering your Q as a string while comparing.

Try the following instead:

function reCalculate(i){

    var Z = document.getElementById, P = parseInt; 

    var qElem = Z("Q"+i);
    var q = P(qElem.value, 10);
    var c = P(Z("C"+i).value, 10);
    var qa = P(Z("QA"+i).value, 10);
    var e = P(Z("E"+i).value, 10);

    q = c - qa;

    if (q < 0) qElem.value = 0;

    if (q < e && q != 0){
        alert(q+" is less than "+e+"?");
        qElem.value = e;
    }

    qElem.value = Math.ceil(q);
}

Upvotes: 4

David G
David G

Reputation: 96810

You are comparing strings not numbers. Use the unary + to convert to a number:

if (+document.getElementById("Q" + i).value < +document.getElementById("E" + i).value ...)

You should use variables by the way:

var input_one = document.getElementById("Q" + i).value,
    input_two = document.getElementById("E" + i).value;

if (+input_one < +input_two) {

}

Upvotes: 0

Akhil Sekharan
Akhil Sekharan

Reputation: 12683

May be you should do a 

parseFloat(document.getElementById("Q"+i).value)

to make sure you are comparing numbers

Upvotes: 1

Snuffleupagus
Snuffleupagus

Reputation: 6715

When you pull the .value of an element it returns a string. '10'<'2' will return true.

You can simply do a parseInt/parseFloat on the value, ala

var q = parseInt(document.getElementById("Q"+i).value,10)

Upvotes: 10

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