Apex: Get all required fields of an sObject

Map<String, Schema.SObjectType> m  = Schema.getGlobalDescribe();
Schema.SObjectType s = m.get('Contact');
Schema.DescribeSObjectResult r = s.getDescribe();
Map<String,Schema.SObjectField> fields = r.fields.getMap();

for(String field : fields.keyset()) {
    Schema.DescribeFieldResult describeResult = fields.get(field).getDescribe();
    if (describeResult.isCreateable()  && !describeResult.isNillable() && !describeResult.isDefaultedOnCreate()) {
        System.debug(field);
    }
}

REST API Response Codes

Apex: Monitor / manage heap during execution

Use the code below in your Apex code to monitor the heap during execution.

System.debug(LoggingLevel.Debug, 'Heap Size: ' + Limits.getHeapSize() + '/' + Limits.getLimitHeapSize());

Reference: https://help.salesforce.com/articleView?id=000170956&type=1

Javascript: Pattern to create instance-specific private data

To make a property private, just make it local to the constructor. Any outside code trying to access age variable will result in an undefined. But the outside code can still call the property that accesses this private variable using the public function getAge.

function Person(name) {

   // Define a variable only accessible inside of the Person constructor
   var age = 25;

   this.name = name;

   this.getAge = function() {
      return age;
   };

   this.growOlder = function() {
      age++;
   };
}

var person = new Person("Nicholas");

console.log(person.name);     // "Nicholas"
console.log(person.getAge()); // 25

person.age = 100;
console.log(person.getAge()); // 25

person.growOlder();
console.log(person.getAge()); // 26

Javascript: Predict the value of this argument

this is determined by the calling context, the way in which function is called.

Calling standalone functions directly

When a function is executed as a simple object function directly, this refers to the global object.

function foo() {
   console.log('Hello World!');
   console.log(this);
}

foo();

Calling functions as property of an object reference

Here we have created an object obj, and there is a property on it which is a function. The function is being called as a property on the object. Here this refers to the object obj itself.

var obj = {};

obj.foo = function() {
   console.log('Hello World!');
   console.log(this);
}

obj.foo();

Calling standalone functions using 'new' keyword

When a function is called using the new keyword, this always refer to the newly created object, an empty object.

function foo() {
   console.log('Hello World!');
   console.log(this);
}

new foo();