How do I determine if a checkbox is checked

Question

For some reason  my form does not want to get the value of a checkbox    I am not sure if it is my coding or not  but when I try and alert   the value  I get undefined as a result  What do I have wrong    lt head gt     lt script gt      var lfckv   document getElementById  lifecheck   checked     function exefunction          alert lfckv            lt  script gt   lt  head gt   lt body gt     lt label gt  lt input id  lifecheck  type  checkbox   gt Lives lt  label gt   lt  body gt    EDIT  I tried changing it to this  function exefunction         alert document getElementById  lifecheck   checked       But now it doesn t even want to execute  What s going wrong

User · Answer

Following will return true when checkbox is checked and false when not.

$(this).is(":checked")

Replace $(this) with the variable you want to check.

And used in a condition:

if ($(this).is(":checked")) {
  // do something
}

User · Answer

x000D   x000D   lt  doctype html gt  x000D   lt html lang  en  gt  x000D   lt head gt  x000D   lt  head gt  x000D   lt body gt  x000D   lt label gt  lt input class  lifecheck  id  lifecheck  type  checkbox  checked  gt Lives lt  label gt  x000D   x000D   lt script type  application javascript   gt  x000D      lfckv   document getElementsByClassName  lifecheck    x000D      if  true     lfckv 0  checked    x000D        alert  the checkbox is checked    x000D        x000D   lt  script gt  x000D   lt  body gt  x000D   lt  html gt  x000D   x000D   x000D    so after you can add event in javascript to have dynamical event affected with the checkbox    thanks

User · Answer

try learning jQuery it s a great place to start with javascript and it really simplifies your code and help separate your js from your html  include the js file from google s CDN  https   ajax googleapis com ajax libs jquery 1 4 4 jquery min js   then in your script tag  still in the  lt head gt   use     function      code inside this function will run when the document is ready     alert     lifecheck   is   checked              lifecheck   change function      do something when the user clicks the box         alert this checked

User · Answer

lt  DOCTYPE html gt   lt html gt   lt body gt       lt input type  checkbox  id  isSelected   gt       lt div id  myDiv  style  display none  gt Is Checked lt  div gt   lt  body gt        lt script src  http   ajax googleapis com ajax libs jquery 1 11 2 jquery min js  gt  lt  script gt       lt script gt              isSelected   click function                     myDiv   toggle this checked                    lt  script gt   lt  html gt

User · Answer

Place the var lfckv inside the function  When that line is executed  the body isn t parsed yet and the element  lifecheck  doesn t exist  This works perfectly fine    x000D   x000D  function exefunction     x000D    var lfckv   document getElementById  lifecheck   checked  x000D    alert lfckv   x000D    x000D   lt label gt  lt input id  lifecheck  type  checkbox   gt Lives lt  label gt  x000D   lt button onclick  exefunction    gt Check value lt  button gt  x000D   x000D   x000D

User · Answer

x000D   x000D  var elementCheckBox   document getElementById  IdOfCheckBox    x000D   x000D   x000D  elementCheckBox 0  checked   return true if checked and false if not checked x000D   x000D   x000D    thanks

User · Answer

You can use this code  it can return true or false    x000D   x000D    document  ready function    x000D     x000D      add selector of your checkbox x000D   x000D    var status     IdSelector   0  checked  x000D     x000D    console log status   x000D   x000D      x000D   x000D   x000D

User · Answer

You are trying to read the value of your checkbox before it is loaded   The script runs before the checkbox exists   You need to call your script when the page loads    lt body onload  dosomething    gt   Example   http   jsfiddle net jtbowden 6dx6A   You are also missing a semi-colon after your first assignment

User · Answer

The line where you define lfckv is run whenever the browser finds it  When you put it into the head of your document  the browser tries to find lifecheck id before the lifecheck element is created  You must add your script below the lifecheck input in order for your code to work

[javascript] How do I determine if a checkbox is checked?

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