javascript "Cannot read property 'checked' of null"

Question

function piliang() {
    var ids = "";
    var num = document.getElementsByName("check");
    for (var i = 0; 1 < num.length; i++) {
        if (num.item(i).checked) {
            ids = ids + num.item(i).value + ",";
        }
        alert(ids);
    }

run successfully

function piliang() {
    var ids = "";
    var num = document.getElementsByName("check");
    for (var i = 0; 1 < num.length; i++) {
        if (num.item(i).checked) {
            ids = ids + num.item(i).value + ",";
        }
    }

This gives out the following error:

"Cannot read property 'checked' of null"

The first code also has this error, but it can run successfully

My English is not good, please try to explain it in code, thank you very much

Both codes look identical so that should not be the case. Could you provide some more info. A good idea will be to print out the value using console.log(num.item(i).checked) — Ulysses
– Ulysses, Commented Nov 9, 2017 at 6:08

mrid · Accepted Answer · 2017-11-09 06:16:07Z

1

Fixed the for loop

function piliang() {
    var ids = "";
    var num = document.getElementsByName("check");
    for (var i = 0; 1 < num.length; i++) {    //use i instead of 1
        if (num.item(i).checked) {
            ids = ids + num.item(i).value + ",";
        }
    }

edited Nov 9, 2017 at 6:16

mrid

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answered Nov 9, 2017 at 6:11

Pratheesh M

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1 Comment

Rajesh Dixit Over a year ago

Just a pointer, this questions qualifies as a typographical mistake. There is a close option for such posts. So its a bad practice to answer such question. You can comment solution under question and if you have enough rep, then even post a close vote.

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