Add checked to element if its attribute value equals to given string

Question

<ul>
    <li>
        <input type="radio" name="letter_type" data-custom="Something" value="0">  Something
    </li>
    <li>
        <input type="radio" name="letter_type" data-custom="Something1" value="1"> Something1
    </li> 
    <li>
        <input type="radio" name="letter_type" data-custom="Something2" value="2" >  Something2
    </li>
</ul>
<script>
    if ($("input[data-custom='Something1']")) {
        alert(true);
        $(this).attr('checked', true);
    }; 
</script>

The list is generated by my PHP (in a loop) script, I wonder why is this not working. I need the Something1 to be checked by default after drawing the list.

JSFiddle example .

Answer 1

try

$("input[data-custom='Something1']").prop( 'checked', true );

DEMO

Answer 2

您不需要if 。

$("input[data-custom='Something1']").attr( 'checked', true );

Answer 3

You need to check the length for if as jQuery always returns an object which has length property, if it doesn't find the element and an object is truthy . Also use prop instead of attr to set the checked value.

var elm = $("input[data-custom='Something1']");
if(elm.length){
   alert(true);
   elm.prop('checked', true);
}