如果在下拉列表中选择了某个字段，如何仅运行JQuery函数

Question

Ok I have a pretty generic state drop down.

<select class="wpcf7-form-control  wpcf7-select wpcf7-validates-as-required required" id="stateid" name="State"><option value="">---</option>
<option value="AL">AL</option>
<option value="AK">AK</option>
<option value="AZ">AZ</option>
<option value="AR">AR</option>
<option value="CA">CA</option>
<option value="CO">CO</option>
<option value="CT">CT</option>
<option value="DE">DE</option>
<option value="DC">DC</option>
<option value="FL">FL</option>
<option value="GA">GA</option>
<option value="HI">HI</option>
<option value="ID">ID</option>
<option value="IL">IL</option>
<option value="IN">IN</option>
<option value="IA">IA</option>
<option value="KS">KS</option>
<option value="KY">KY</option>
<option value="LA">LA</option>
<option value="ME">ME</option>
<option value="MD">MD</option>
<option value="MA">MA</option>
<option value="MI">MI</option>
<option value="MN">MN</option>
<option value="MS">MS</option>
<option value="MO">MO</option>
<option value="MT">MT</option>
<option value="NE">NE</option>
<option value="NV">NV</option>
<option value="NH">NH</option>
<option value="NJ">NJ</option>
<option value="NM">NM</option>
<option value="NY">NY</option>
<option value="NC">NC</option>
<option value="ND">ND</option>
<option value="OH">OH</option>
<option value="OK">OK</option>
<option value="OR">OR</option>
<option value="PA">PA</option>
<option value="RI">RI</option>
<option value="SC">SC</option>
<option value="SD">SD</option>
<option value="TN">TN</option>
<option value="TX">TX</option>
<option value="UT">UT</option>
<option value="VT">VT</option>
<option value="VA">VA</option>
<option value="WA">WA</option>
<option value="WV">WV</option>
<option value="WI">WI</option>
<option value="WY">WY</option>

What I want to do is run a JQuery script ONLY if a certain value is selected from the drop down.

This is the code I have so far, but it's not working

if(#stateid.wpcf7-form-control=='AL') {
jQuery(function($){
$("input[name=phone]").mask("(999) 999-9999? ext.99999");
})
}; 

Anyone care to help as why it's not working?

Answer 1

You need to put the condition in the event handler instead of putting event handler in condition.

Live Demo

jQuery(function($){    
   $('#stateid').click(function(){
        if($(this).val() =='AL') {
           $("input[name=phone]").mask("(999) 999-9999? ext.99999");
        }  
    });
}); 

Here is the syntax for click event handler.

$("selector").click(function() {
   //You code here, your condition 
});

You can learn more about selectors here ;

Answer 2

Why is it not working?

Where did you learn about #stateid.wpcf7-form-control ? That is a syntax error.

Select an element

var select = $("#stateid.wpcf7-form-control");

add onchange event

select.on("change", function(){

});

get the value

select.val();

Answer 3

If you only want the mask to be applied when one particular option is selected and not for the other options then you may also need a way to clear the mask if a user selects an option not equal to AL afterwards.

You could use a function triggered off the the JavaScript .blur() event to execute the logic of whether to set or clear the mask on the input.

$(function() {
    $('#stateid').on('blur', function() { // hook in your custom function onto the element with id = stateid
        if (this.options[this.selectedIndex].value === 'AL') { // check which option is selected
            // set mask
        } else {
            // clear mask
        }
    });