javascript如果条件&&条件不起作用

Question

the AND && operator doesn't work, but when i replace it with an OR || operation it is workin, why? I just used OR || operator for testing, what i need is an && operator. Please help. thanks

function validate() {
    if ((document.form.option.value == 1) && (document.form.des.value == '')) {
        alert("Please complete the form!");
        return false
    } else return true;
}

i also tried nested if but it doesn't work too

    if(document.form.option.value==1)
    {
         if(document.form.des.value=='')
        {   
            alert ("Please complete the form!");
            return false

        }
    }   

Answer 1

It sounds like || is what you are looking for here. The && operator is only true if both the left and right side of the && are true. In this case you appear to want to display the message if the value is 1 or empty. This is exactly what the || operator is for. It is true if either the left or right is true

Answer 2

If Or operator is working, means there are some javascript errors in your second part of condition. check document.form.des.value=='' (maybe just open your javascript console in Chrome/Firefox/IE8+)

Answer 3

its because one of the conditions specified above returns false and loop breaks. Is you use OR ,only one must be validated and returns true.. check your code for both the conditions.