html - Autocheck checkboxes in javascript -

html - Autocheck checkboxes in javascript -

i have multiple checkboxes on page , "select all" button.i want ,that when press select button, elements on page checked.this javascript code have tried:

class="snippet-code-js lang-js prettyprint-override"><script> function selectall() { (var = 0; < document.getelementsbyname("ch").length; i++) { document.getelementsbyname(ch[i]).checked = true; } } </script>

and here' html: class="snippet-code-html lang-html prettyprint-override"><form action="analize.php" method="post" enctype="multipart/form-data"> <input type="button" onclick="selectall()" value="select all" /> <input type="checkbox" name="ch[]" value="a" align="midle" /> <input type="checkbox" name="ch[]" value="b" align="midle" /> <input type="checkbox" name="ch[]" value="c" align="midle" /> </form> don't work.what problem?

the name attribute of target elements ch[] not ch. .getelementsbyname(ch[i]) should .getelementsbyname('ch[]')[i].

for (var = 0; < document.getelementsbyname("ch[]").length; i++) { document.getelementsbyname('ch[]')[i].checked = true; }

you cache nodelist more efficient querying dom in each iteration:

var nodelist = document.getelementsbyname("ch[]"); (var = 0; < nodelist.length; i++) { nodelist[i].checked = true; }

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