How to get field values ECMA Script/Javascript using CSOM?

In this below script,get field values ECMA Script/Javascript using CSOM

SharePoint client object model used to retrieve, update, and manage data in SharePoint 2013.


Types:
1.Server Object Model
2.Client Object Model
3.Javascript Library
4.Rest Service/OData Library

Loads the SP.Runtime.js and SP.js files by using the getScript function in jQuery.


Title – SP.ListItem.get_item('Title');

ID – SP.ListItem.get_id();

Url -SP.ListItem.get_item('urlfieldname').get_url()

Description – SP.ListItem.get_item('descriptionfieldname').get_description();

Current Version – SP.ListItem.get_item("_UIVersionString");

Lookup field – SP.ListItem.get_item('LookupFieldName’).get_lookupValue(); // or get_lookupID();

Created By – SP.ListItem.get_item("Author").get_lookupValue();

Modified by – SP.ListItem.get_item("Editor").get_lookupValue();

Choice Field – SP.ListItem.get_item('ChoiceFieldcolumnName');

Created Date – SP.ListItem.get_item("Created");

Modified Date – SP.ListItem.get_item("Modified"); -> case sensitive does not work with 'modified’

File  – SP.ListItem.get_file();

File Versions -  File.get_versions();.

Content Type – SP.ListItem.get_contentType();

Parent List – SP.ListItem.get_parentList();

Note:  ('LookupFieldName’).get_lookupValue() sometimes returns an array of data, especially when your lookup allows multiple values.
For this,you will need to iterate the array and get each value individually.

 SP.ListItem.get_item('LookupFieldName’)[0].get_lookupValue();

For Arrays:


       for(var i = 0; i < oListItem.get_item("LookupFieldName").length; i++)
 {
      alert(oListItem.get_item("LookupFieldName")[i].get_lookupId()); // or get_lookupValue()
 }