onsubmit multiple javascript functions

问题:

Does anyone know how to onsubmit multiple functions? What I intented to do was: onsubmit checks if all these functions return true, if all of them return true, then I do the action="checked.html"

<form id="myForm" name="myForm" action="checked.html" method="post"
onsubmit="return validateName() || validatePhone() || validateAddress() ||
validateEmail()">

However, what actually happened was, the computer checks the code from left to right, and the result of the next function will replace the previous one, and so on, until the end. So, even if all the 3 first functions return false, as long as the last one is true, the computer will execute action="checked.html", which is not what I intented to do... can anyone please help me on this, it's been like 4 hours I'm trying to fix it :S Thanks!

Also, when I tried to do something like <form onsubmit="return verify1() && verify2()">, it doesn't work, all it does is to check verify1(), and not the following ones... :(

CLARIFCATION: On submit, I want four validation functions to be called. Submit should be prevented unless all four functions return true, but all four should always be called even if some of them return false.

回答1:

Use & instead of &&.

&& uses short-circuit evaluation and so doesn't evaluate the right-hand operand if the left-hand operand is falsy.

& always evaluates both operands.

onsubmit="return !!(validateName() & validatePhone()
                      & validateAddress() & validateEmail());"

EDIT: Sorry, I forgot that & won't return an actual boolean. Wrap the expression in parentheses and use a double ! to convert it as (now) shown. (You wouldn't need to worry if using the result in an if test, but the return value from the event handler should be an actual boolean.)

P.S.: Here's a rather clunky demo to show that all four functions get called but produce the overall true or false result that you need: http://jsfiddle.net/nnnnnn/svM4h/1/

回答2:

Change your code to use AND instead of OR

onsubmit="return validateName() && validatePhone() && validateAddress() && validateEmail()"

The reason being that if you use OR once that first function returns true javascript won't bother to check the other functions. Also you don't want to use OR because if the first check was false and second is true the form will still submit since at least one of your checks is TRUE.

See fiddle to show this works, both checks execute and show an alert message but because check2 returns false the form doesn't submit - if you want play around with the return results of checks1 and check2 functions and the use of && and ||

After understanding the problem better, you need to use a single &, but because true & true returns 1 and not true you need to write it like this

onsubmit="return ((validateName() & validatePhone() & validateAddress() & validateEmail()) == 1)"

回答3:

if all you need is make sure all functions return true before proceeding, then use && not || and to insure that the expression does not get evaluated pre-maturally by the return function put some extra brackets

<form id="myForm" name="myForm" action="checked.html" method="post"
onsubmit="return (validateName() && validatePhone() && validateAddress() &&
validateEmail() )">

回答4:

Create a wrapper function, which call each function and checks their return value. At any time if the return value is false you can either stop the form submit by returning false at that time or evaluate the rest of the things and finally return false.

So JS a code that will do what you want is :

function validateForm() {
    var isFormValid = true;
    isFormValid &= validateName();
    isFormValid &= validatePhone();
    isFormValid &= validateAddress();
    isFormValid &= validateEmail();
    return isFormValid? true:false;
}

Now in the form simply use :

<form id="myForm" name="myForm" action="checked.html" method="post" onsubmit="return validateForm();">

Here is a working JSFiddle Example.

EDIT : Made a boo boo below, corrected.

Using OR was incorrect, but the reason AND is not working how you are expecting is because of Short-circuit_evaluation.

OR : Evaluation stops on first operand which is true and true is returned

AND : Evaluation stops on first operand which is false and false is returned

回答5:

onsubmit="return validateName() && validatePhone() && validateAddress() && validateEmail()"

use this code

回答6:

To validate my form I simply created a function called validateForm(){} then inside this function I put all the code which is needed for full validation. Then used onsubmit="validateForm()". It checks through it in order and only submits if all conditions are true.

回答7:

Following method check first validateName() function and it will process to check next function if only first function is true, also to fire third function need to return true of first & second function. So just imagine if all function are invalid & even you have different error message, you will see only error message of first function. Once validateName() function pass, you may see the error message of validatePhone() ect.

<form id="myForm" name="myForm" action="checked.html" method="post"
onsubmit="return (validateName() && validatePhone() && validateAddress() &&
validateEmail() )">

You can't use above if you going to show error messages according to above all validations on first submit & you can use following method if you want to fire all function (or display all validation errors) on submit.

<form id="myForm" name="myForm" action="checked.html" method="post"
onsubmit=" if( ( validateName() && validatePhone() && validateAddress() &&
validateEmail() ) == false) { return false; } ">