javascript - How to get an alert to appear when a certain option is selected from the dropown menu -

i'm trying display alert user when select option dropdown menu, depending on option chosen different alert display. have far

function tagchange(dropdown) {    (var i, x = 0; = dropdown.options[x]; x++) {      if (i.value == "a") {        alert("you've clicked a");      }    }  }

<select onchange="tagchange(this);" name="topic">            <option disabled selected value> -- none selected -- </option>            <option value="a">a</option>            <option value="b">b</option>            <option value="c">c</option>        </select>

it shows alert every option clicked, not one.

directly use dropdown.value .for loop not necessary .

note *: dont forget add bracket in function open , close function(){ }.you missing { in function start

function tagchange(dropdown) {    if (dropdown.value == "a") {      alert("you've clicked a");    }    }

<select onchange="tagchange(this);" name="topic">        <option disabled selected value> -- none selected -- </option>        <option value="a">a</option>        <option value="b">b</option>        <option value="c">c</option>    </select>