Difference between revisions of "JQuery - Tips"

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<accesscontrol>Main:MyGroup</accesscontrol>
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[[Category:Miscellaneous]]
 
== JQuery Tips ==
 
== JQuery Tips ==
'''1. Optimize performance of complex selectors'''<br>
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var subset = $("");
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'''1. Optimize performance of complex selectors'''<br/>var subset = $(""); $("input[value^='']", subset);''<br/><br/>'''2. Set Context and improve the performance'''<br/>On the core jQuery function, specify the context parameter when. Specifying the context parameter allows jQuery to start from a deeper branch in the DOM, rather than from the DOM root. Given a large enough DOM, specifying the context parameter should translate to performance gains. $("input:radio", document.forms[0]);<br/><br/>'''3. Live Event Handlers'''<br/>Set an event handler for any element that matches a selector, even if it gets added to the DOM after the initial page load: $('button.someClass').live('click', someFunction);<br/><br/>'''4. To show / hide element'''
$("input[value^='']", subset);
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<br>
 
<br>'''2. Set Context and improve the performance'''<br>
 
On the core jQuery function, specify the context parameter when. Specifying the context parameter allows jQuery to start from a deeper branch in the DOM, rather than from the DOM root. Given a large enough DOM, specifying the context parameter should translate to performance gains.
 
$("input:radio", document.forms[0]);
 
<br>
 
<br>'''3. Live Event Handlers'''<br>
 
Set an event handler for any element that matches a selector, even if it gets added to the DOM after the initial page load:
 
$('button.someClass').live('click', someFunction);
 
<br>
 
<br>'''4. To show / hide element'''<br>
 
 
  $("a").hide();
 
  $("a").hide();
  $("a").show();
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$("a").show();
<br>'''5. Check element exists'''<br>
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<br/>'''5. Check element exists'''
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  if ($("#someDiv").length) {}
 
  if ($("#someDiv").length) {}
<br>'''6. Back to top button/link'''<br>
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<br/>'''6. Back to top button/link'''
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  $('#top').click(function() {   
 
  $('#top').click(function() {   
  $(document).scrollTo(0,500);  }
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$(document).scrollTo(0,500);  }
<br>
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<br>'''7. Change width of item on many browser'''<br>
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<br/><br/>'''7. Change width of item on many browser'''
  $('#item').width(500);
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<br>
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  $('#input:text[name=QUESTION.Q12.1]).width(500);
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<br/><br/>var error_message = "The error was happened" var oldCheck = questioncheck; questioncheck = function() {
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  //QUESTION.Label1
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  if (checkLength("QUESTION.Label1",5)){
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    ErrorMessages.getInstance().clearErrorMessages();
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    ErrorMessages.getInstance().showErrorMessage(error_message);
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    return;
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  }
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}
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function checkLength(objname,maxlength) {
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  var ao=$("input:text[name="+objname+"]");
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  if (ao.val().length>maxlength)
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    return true;
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  return false
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}<br/><br/>'''8. Get value of question in javascript'''<br/>from_Q8= "{{Q8[0].value}}";

Latest revision as of 11:39, 23 October 2013

<accesscontrol>Main:MyGroup</accesscontrol>

JQuery Tips

1. Optimize performance of complex selectors
var subset = $(""); $("input[value^=]", subset);

2. Set Context and improve the performance
On the core jQuery function, specify the context parameter when. Specifying the context parameter allows jQuery to start from a deeper branch in the DOM, rather than from the DOM root. Given a large enough DOM, specifying the context parameter should translate to performance gains. $("input:radio", document.forms[0]);

3. Live Event Handlers
Set an event handler for any element that matches a selector, even if it gets added to the DOM after the initial page load: $('button.someClass').live('click', someFunction);

4. To show / hide element

$("a").hide();
$("a").show();


5. Check element exists

if ($("#someDiv").length) {}


6. Back to top button/link

$('#top').click(function() {  
$(document).scrollTo(0,500);  }



7. Change width of item on many browser

$('#input:text[name=QUESTION.Q12.1]).width(500);




var error_message = "The error was happened" var oldCheck = questioncheck; questioncheck = function() {

  //QUESTION.Label1
 if (checkLength("QUESTION.Label1",5)){
    ErrorMessages.getInstance().clearErrorMessages();
    ErrorMessages.getInstance().showErrorMessage(error_message);
    return;
 }
 

}

function checkLength(objname,maxlength) {

  var ao=$("input:text[name="+objname+"]");
 if (ao.val().length>maxlength)
    return true;
 return false

}

8. Get value of question in javascript
from_Q8= "{{Q8[0].value}}";