php内部的Javascript函数

Question

I try to create a button in php and increase or decrease its value (inside the text input) on click.

<?php

echo "<script>
    function inc(elem)
    {
        x = elem.value;
        //alert('dsadasdasdsadasdas');
        if(x<31)
        {
        x= x+1;
        }
        alert(x);
        elem.value = x;
    }
    </script>";

            echo '<form action="tziros.php" method="post">';
            echo '<input type="text" value="1" name="tziros_imeras">';
            echo '<br>';
            //echo '<input type="button" value="ADD +" onClick="inc(document.getElementById("tziros_imeras"))">';
            echo '<input type="button" value="ADD +" onClick="inc(document.getElementById(\'tziros_imeras\'))">'
            //echo '<input type="button" value="DEC -" onClick="dec();">';  
            echo '<input type="submit" name="submit_tziros_meras" value="OK">';
            echo '</form>'; 
?>

Problem is that javascript is not running at all .

EDIT : after reading your answers i came up with this: js:

 function inc(elem)
        {
        elem.value++;
        }

and on the form:

echo '<input type="text" value="1" id="tziros_imeras" name="tziros_imeras">';

So now at last, the js is running .

Answer 1

• You're looking for tziros_imeras by ID (getElementByID) but you have only the name property set up to tziros_imeras

• you have only the method inc() - you're missing the method dec()

and most important:

• you're incrementing x which is a local variable (it doesn't affect the actual element), you should do instead:

  elem.value += 1;