How to use standard Salesforce REST API from Salesforce Visualforce Page?

Befor any Ajax call, make sure to add ‘Bearer’ token in header. If using JQuery use below code snippet.

$.ajax({
type: reqType,
beforeSend: function (xhr)
{
xhr.setRequestHeader("Authorization", 'Bearer {!$API.Session_ID}');

},
headers : {'Content-Type' : 'application/json; charset=utf-8'},
url: postUrl,
data: postData,
dataType: 'text'
})
.done(function( data ) {
//Code if success
})
.fail(function(xhr,textstatus,error){
//Code if fail
});