jQuery Ajax从表单发送数据不起作用

Question

My script should prevent the page to be refreshed or redirected, but when i click submit button it redirects me.

Error Message from JavaScript console

Uncaught TypeError: $(...).val(...).len is not a function

myScript.js

$( document ).ready(function() {
    console.log( "Ready!" );
    //Submitting the form data
    $("#user-form").submit(function(e){
        if($('#fName').val().len() != "" && $('#lName').val().len() != "" && $('#nickname').val().len() != "") {
            $.ajax({
               type: "POST",
               url: "user-process.php",
               data: $("#user-form").serialize(),
               success: function(data){
                   $('#user-form')[0].reset();
                   console.log(data); // show response from the php script.
               }
             });
         }
         else {
             alert("Please fill the fields.")
         }
        e.preventDefault();
    });

    setInterval(function(){ $(`#table`).load('info.php #table'); }, 1000); //Loading table data without refreshing page.

});

Answer 1

尝试使用.length而不是.len（） https://api.jquery.com/length/

Answer 2

val() returns a string. Strings don't have .len() function. Also, since you're comparing it with another string, you don't need to get length, just use this:

    if($('#fName').val() != "" && $('#lName').val() != "" && $('#nickname').val() != "") {

If you want to check length, you can get it using .length . But then you should compare it with 0 , not with "" :

    if($('#fName').val().length != 0 && $('#lName').val().length != 0 && $('#nickname').val().length != 0) {

Things like $('#fName').val().length != "" would technically work, because JavaScript will convert "" into 0 for you, but it's a bad coding practice, as it makes the code hard to follow.

Answer 3

To know if a string is empty or not, you can use the following statements :

• $(selector).val() !== ''
• !$(selector).val().length
• $(selector).val().length === 0

(Since a string length will never be negative, the two last ones are equal)

About the redirection fact, take a look at the stopPropagation and stopImmediatePropagation functions

https://api.jquery.com/event.stopimmediatepropagation/ https://api.jquery.com/event.stoppropagation/

Answer 4

"len()" is not a javascript function, you can modify your code to be :

if( $('#fName').val() && $('#lName').val() && $('#nickname').val() )

and will work

Answer 5

In JavaScript, String object don't have len() function, instead they have length property.

Usage:

var myString = "Hello";
console.log(myString.length); // returns 5