Question

90

Cannot read property 0 of null

rated 0 times [ 91] [ 1] / answers: 1 / hits: 48515 / 11 Years ago, mon, february 3, 2014, 12:00:00

I get this error Cannot read property '0' of null.

I have a table with

somename.html

<table>  

    <tr>  

    <td id=td1>text</td>  

    </tr>  

    </table>

somename.js

function test(){  

    var date=new Date();  

    if(date.getDay()==1 && date.getHours() >=13  && date.getMinutes() >=3 ){ //8-9AM  

        document.getElementById('td1')[0].style.color = 'blue';  

    }else if(date.getDay()==1 && date.getHours() == 14  && date.getMinutes() <= 20){  

            document.getElementById('td1')[0].style.color = 'blue';  

    }else{  

      //nothing  

    }  

}  

setInterval(test(),1000);

EDIT: new error if i remove [0] Cannot read property 'style' of null

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amari

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answered 11 Years ago americar · Accepted Answer

getElementById returns null if there is no match in the document. (Which then leads to exactly your error message).

This means that either you have a typo in your selector or the html or the js gets executed before your element is included into the dom.

Also, getElementById returns a single element and not an array (Node List to be precise), so the correct call would be:

document.getElementById('td1').style.color = 'blue';

Third problem:

setInterval(test(),1000);

//              /

// this will immeditately execute the function and

// hands over the *return value* to setInterval

will not work as intended, it needs to be

setInterval(test,1000);

//            /

// hand over the *function reference* to be executed after 1 second

Cannot read property *0* of null

Answers

amari

Cannot read property 0 of null