AuraHandledException

From Apex class:

 @AuraEnabled

    public static List<Account> fetchAccount() {

        throw new AuraHandledException('User-defined error');

    }

From client-side controller:

doInit: function(component, event, helper) {

        var action = component.get('c.fetchAccount');

        action.setParams({ firstName : cmp.get("v.firstName") });

        action.setCallback(this, function(response) {

            var state = response.getState();

            if (state === "SUCCESS") {

                component.set('v.Accounts', response.getReturnValue());

            }

            else if (component.isValid() && state === "ERROR") {

                console.log("Error Message: ", response.getError()[0].message);

            }

        });

        $A.enqueueAction(action);

    }

How to Select All Fields with SOQL in Apex

1. Query All Fields for a Known Record ID:

ID recordId = '5001a00000CgCE2';

DescribeSObjectResult describeResult = recordId.getSObjectType().getDescribe();

List<String> fieldNames = new List<String>( describeResult.fields.getMap().keySet() );

String query =
  ' SELECT ' +
      String.join( fieldNames, ',' ) +
  ' FROM ' +
      describeResult.getName() +
  ' WHERE ' +
      ' id = :recordId ' +
  ' LIMIT 1 '
;

// return generic list of sobjects or typecast to expected type
List<SObject> records = Database.query( query );

System.debug( records );

2. Query All Fields for All Records

The same concept as above but we don’t have a specific record ID, so we need to determine the sobjectype by explicitly specifying the object we’ll query on.

// without an ID, simply specify the object to then derive the sobject type
DescribeSObjectResult describeResult = Account.getSObjectType().getDescribe();

List<String> fieldNames = new List<String>( describeResult.fields.getMap().keySet() );

String query =
  ' SELECT ' +
      String.join( fieldNames, ',' ) +
  ' FROM ' +
      describeResult.getName()
;

// return generic list of sobjects or typecast to expected type
List<SObject> records = Database.query( query );

System.debug( records );

JavaScript in Strict Mode

JavaScript code that runs in a browser can access a user's private information. To protect this information, LockerService requires you to use ECMAScript (ES5) strict mode, and enforces it in your code. This mode makes it easier to write secure JavaScript. A few code tweaks to comply with ES5 can substantially reduce the need for checking data at runtime.

Here’s a simple example of how strict mode prevents JavaScript from traversing the call-stack and modifying other functions. Without strict mode, the following function would have returned the name of the function that called primaryFunction().

JavaScript code:
function primaryFunction() {
  'use strict'
  console.log("The function calling the current method is: “+ primaryFunction.caller.name);
}
function callerFunction() {
  return primaryFunction(); 
}
callerFunction();

Output:
Uncaught TypeError: 'caller' and 'arguments' are restricted function properties and cannot be accessed in this context.
at primaryFunction (<anonymous>:3:72) at callerFunction (<anonymous>:6:10) at <anonymous>:8:1

Strict mode restricts access to several other entities. When it is enforced, you can no longer reference the window object through the JavaScript variable this, for example. These restrictions eliminate a lot of potential security vulnerabilities.

List of Annotations in Salesforce Apex

Usually Annotation means which will specifies the behavior or modifies the way how the particular class or method behaves in salesforce. Based on annotations the functionality or behavior and usage of particular class or method we can simply identify.

Each annotation will starts with '@' symbol and followed by name of the annotation
To declare a method/class with annotations it must be declared immediately before method/class

List of Available Annotations in Apex:

• @isTest
• @InvocableMethod
• @InvocableVariable
• @future
• @AuraEnabled
• @ReadOnly
• @RemoteAction
• @TestSetup
• @TestVisible
• @Deprecated

Apex REST annotations:

• @RestResource(urlMapping='/yourUrl')
• @HttpDelete
• @HttpGet
• @HttpPatch
• @HttpPost
• @HttpPut

How To Allow Only Numbers in Phone Number Field in Visual Force Page

If your trying to restrict your phone number field to accept only Numbers in visual force page you can use the below simple JavaScript code to achieve this easily.

<script>

function isNumber(evt) {
        evt = (evt) ? evt : window.event;
        var charCode = (evt.which) ? evt.which : evt.keyCode;
        if (charCode > 31 && (charCode < 48 || charCode > 57)) {
            return false;
        }
}

</script>

<apex:inputfield value="{!c.Phone__c}" id="boPhone" onkeypress="return isNumber(event)"/>